beat martyr and the expansion, prophecy. overall, a really enjoyable experience and worth the money (i think i got it for $25 on sale?). story-wise, it was actually pretty interesting, even if you're not a super WH40k lore nerd. but it does take a bit to get going.
things i liked:
the mission structure breaks the game up into approachable chunks
nailed the grimdark feel, and the enemies are faithfully recreated from the tabletop
sense of scale - things that are big and scary on the tabletop are correspondingly big and scary in the game
some really fun missions where you get to take control of big mech things
leveling occurs pretty quickly, and spells/passive buffs are unlocked at a nice pace.
graphically beautiful
items granting skill slots or certain abilities i thought was a pretty interest change to the normal "gearing" of an ARPG game
"supression" buff/debuff system is an interesting take on when/how your character gets CC'd
"intel" missions, found in game, are extra challenging and extra-rewarding
things i didn't like:
limited items - items are class-specific, which i felt really limited potential opportunities
most enemies just run at you - so limited combat mechanics, at least for my psyker.
big mech things make the big mech missions too easy (despite being fun to blow stuff up). also missed opportunities for kaiju fights
i think the difficulty curve fell off a bit at the end except for boss fights, which were still quite deadly/punishing.
i didn't delve into the endgame content, which people who like D3 Grifts and things will probably appreciate more than me. i felt that Martyr was best when it threw lots of enemies types at you from different directions, with a boss/champion in the mix to really make you choose who to attack. if you're an ARPG fan, this might be a nice change of pace from the hyper-fast action of PoE or Diablo3