I waited until I beat the game before I made a review, though it was tempting at times to just jump in and say how good the game is. I have a summary at the top, followed by a section that goes in detail. The detailed section was too long, so I put the last bit in a comment on this review.

In short, the game is easily a 9 to a 9.5 out of 10 for me. I had played Owlcat's previous two games and love them all, so I got really excited when I heard about this one back when it was announced. I was ecstatic when I got it for Christmas (so technically not for free in terms of some sort of sale, but functionally free and still 100% worth full price). The story is good, though I had a few bugs here and there (and Owlcat has released many fixes during the time I've been playing) and though some Aeldari bits seemed a tad too sensationalist. The build crafting is satisfying (allowing me to kill the final boss in one round on max difficulty; I'm still enjoying the adrenaline rush from that right now). The combat is tactical and really makes positioning and knowing when to use each of your characters' skills important, but it also had me cackling (or maniacally giggling, your choice) when I got builds and tactics to line up right. So, 9 for the story, 9.5 for the build crafting, and 10 for the combat, which brings me to a 9.5 average. Below, I have included a bigger breakdown of the positives and negatives of each. There may be very mild spoilers in the story section.

Story:
First with the negatives: This game is so Warhammer 40k that the dialogue options can be a bit limiting. I really love how 40k the game looks and sounds and feels, and how that affects dialogue 90-95% of the time, but I did get mildly annoyed a couple times at a character being an idiot or dialogue options not including how I would respond but at best making me sound like a rich idiot whose palm is glued to his handheld mirror or at worst making me sound like a genocidal maniac who flushes his toilet with the blood of orphans. In between, you happen to have the genocidal maniac who makes a mountain of corpses because orbital bombardments sound cooler than listening to people's problems. Again, this game is very Warhammer 40000, and I normally really like that. Story also does affect game mechanics to some degree, with the alignment system (non-traditional here with two variants of self-righteous scumbags and one dude who gets ostracised for being nice--which I do find somewhat funny) giving you benefits as you progress along each path. However, reaching the max rank with an alignment before the final boss is difficult; for instance, I achieved max rank Iconoclast (the closest to not being a constant dirt-wad) literally in my last decision in the game, so I never had a chance to benefit from its amazing perk--friendly fire immunity, basically. RIP teamkills.

Despite all this, I found myself investing again and again into the characters, and by the end I was rooting for characters I initially did not care for much. For example, I did not really like Heinrix but suddenly found myself appreciating him due to his character arcs and development as a person, and I was mentally cheering for him in the dialogue before the second last fight in the game. The character writing really made me love this game's story, and it coupled well with the feel of it--trust me and listen to the ost, even just the Reaving Tempest theme song. I did read someone's complaints that characters do not react as much to your actions as in previous games by the devs, specifically Pathfinder: Wrath of the Righteous, and while I can see why, I think the story is still good on its own, without comparison to WotR, which had a TON of player options (though Rogue Trader has a lot of options by any normal RPG's standards) and has had much fine-tuning through updates and such. The general plot is also good, but the final act could have used a bit more prefacing or hinting. Even so, if you don't just rush through dialogue, you can encounter quite a good tying together of plot lines, especially in the end dialogues (before the second last fight and before and after the last fight) and in the epilogue, which tells you what happened to all the worlds and major characters. I got so lost in the story that I did what I do with books and take a freaking AGE getting through the last 10-30min, dragging it out so it wouldn't end. I haven't done that with a game since I played Transistor and Pyre in 2021, and Transistor has long been my favourite story game. I recorded the final companion dialogue, the final mission, the dialogues with bosses, the final decisions I made, and the epilogue, all the while going through it painfully slowly to torture myself with the fact that the story was coming to a close--like I do with books I really enjoy. The story gets a 9/10 for me, though I WISH I could give it a 10.

The build crafting is complex. You choose an origin (your background), a type of origin world (like agri-worlds or forge worlds... etc.), and then one of four primary classes. Maxing out your primary class gives you access to one of three secondary classes--though there are more than three secondary classes; each primary class locks you into a choice between three of them only. Then you get the exemplar class, the only tertiary class. You can take passives and abilities from your previous two classes as well as absolutely game-destroying perks specific to exemplar. I will not name names as I do not want my boy nerfed more than he has been (RIP flat damage from Versatility, you will be missed, though you were definitely too insane to live). The origin stuff (world of birth and starting vocation) give you access to passives you can get when levelling, which can make a MASSIVE difference, especially considering being a psyker is bound to origin (original vocation, specifically) rather than class and benefits from a lot of perks other systems would just have benefit non-magical abilities and damage instead (like Run and Gun letting you cast more spells instead of only letting you shoot more).
See the rest in the comments, if you want.

Also, levelling up is FAR quicker than in any other CRPG I have played as the level cap is 55 instead of 20, and every level-up is useful (no only getting a little bit of HP for levelling up), though useful to varying degrees. The build system is fairly complex--though what else would you expect form developers who made two games on the 1st edition Pathfinder system?--and allows for you to progressively learn what does and doesn't work while doling out some absolutely broken, boss-shredding annihilation. You can build so well that you can kill the final boss in one round on the max difficulty with only one character doing damage and with killing all secondary enemies before the boss. It is so satisfying; it has made me cackle and giggle like I was once again the little boy who laughed loudly on seeing the size of a heavy weapon in the original Star Wars Battlefront 2 (true story). I have heard of people struggling with builds, but you can also just ask people on the discussions page; I have gotten some good pointers (such as that burst fire attacks do not count as area attacks for some reason), and I am sure that some youtubers have probably made builds. I don't know that for sure as I prefer to make my own builds, usually. As for how intuitive the buildcrafting is, this is the first Owlcat game where I made the builds for all my characters myself; the previous two games (Pathfinder Wrath of the Righteous and Kingmaker), I only made about half of the builds myself (or at least took inspiration from others for the second half). This system seems more easily understood than that of the previous two game by Owlcat, though I do really love those games and highly recommend them. I even have a half-backed madman's plan of using the same origin details and classes and whatnot to make a COMPLETELY different playstyle. I think the build crafting deserves a 9.5/10. I only don't give it a 10 because there are so few classes right now, especially compared with Kingmaker and WotR and considering that you have six characters in a party, though dlc classes will be added later. The fact that they can get such build diversity with as few classes as they have is impressive.

The combat itself is fairly standard for a turn-based crpg: position and shoot. However, the way Owlcat makes this different makes it great. Passives can work out in so many different ways that just fit in seamlessly. Do you want to avoid damage? You can dodge, or parry, or use cover (with multiple cover types), or use armour (with multiple damage reduction stats). I feel like I am playing a tabletop and ARPG hybrid, and I love that. Cover has health and different levels of cover can affect you differently. Armour reduces damage by a percentage, but deflection reduces it by a flat amount, applied after armour. Both parrying and dodge chances can apply against a melee attack. Bonus hit chance becomes crit chance. There are just so many neat things that work together so well. Weapon types really matter. Oh, you like guns? Do you want solid projectiles or laser projectiles? How about plasma or flamers or melta (flamer on steroids)? You want melee? How about a sword? No? How about one with a chainsaw blade (a standard of Warhammer 40000), or one wreathed in lightning that cleaves your enemies? No? How about you just be a witch and get a sword you can empower with force, you Lovecraftian freak? Still no good? Okay, get the magic shiny sticks and go bonk with chain lightning. Enjoy. Every. Single. Weapon type has something under the hood that makes it worthwhile. Solid projectiles pierce targets well (RIDICULOUSLY well). Laser projectiles are harder to dodge. Going through them all would take too long.

And on top of that, the developers have added quality of life improvements over their previous game which really fit with the flavour of Warhammer 40k. The health system is amazing; you immediately recover to full HP after a fight but can incur injuries which can stack to become traumas (debuffs that last with you until you get back to your ship or find some other (rare) way of healing them). This allows for meaningful impact from dying and taking too much damage without having to stress about healing. There are also no spell slots but rather destabilisation of reality that comes with spells (which is an interesting take on the original TTRPG's system, and I like it). You also do not have to spend ten minutes buffing yourself like some builds in Kingmaker and Wrath of the Righteous require. Buffs can only be cast in fights, which makes action point management (as in games like Divinity: Original Sin 1 and 2) important. I could keep going, but you can tell from this that I really like the combat system and how it interacts with buildcrafting. This game deserves a 10/10 for the combat system. The only downside is that the space combat is rough early game and can glitch out and refuse to turn your ship sometimes. That is legitimately my only complaint for the combat.

TLDR: 9/10 for story; 9.5/10 for build crafting; 10/10 for combat. This is 100% worth the full price.

PS: There are optimisation issues. Check one of the first comments in this thread for an example.