I really enjoyed this game. It plays very differently from a lot of turn-based tactics games, and some of the mechanics are quite original - for example, there's no RNG element to your chance to hit a target, you can either hit it or you can't, and instead of each character having a set allowance of action points per turn, the squad relies on a shared pool of points which you can get from defeating enemies or from certain points on the map (which adds another tactical element of controlling key points). It feels much more like controlling an actual squad of soldiers instead of a party of individual heroes, as they are all co-ordinating together and setting things up for each other, it fits the setting perfectly.
The progression of unlocking new tools and weapons is really satisfying. At the start you will be using very basic pistols and melee weapons, by the end you'll be blasting whole squads of enemies at a time with flamethrowers and arc weapons. I like the skill trees as well, you can specialise or cross-class as much as you like, and there are lots of different skills and branches to experiment with.
The art style and atmosphere are amazing, and the soundtrack is also very original and fits the setting perfectly. The combination of the music and the rhythm of combat is mesmerising.
Last of all I enjoyed the writing, with the tech priest characters there's a danger of them being too robotic to relate to, but the writing avoided this. While the sound-design emphasises their mechanical nature, each character is different, with different concerns, motivations and ways of speaking, and that adds a lot of depth. Ironically some of the tech priests in this game are more individual and emotive than the humans in other 40k games. The necron bosses are also great, they have very dramatic fully voiced dialogue in contrast to the tech priests (and the mindless drone necron soldiers), and it gives them so much personality, each boss encounter feels special.