I heard some fairly dodgy reviews of this game, especially from the US game websites, but Dark Messiah has an awful lot going for it. For me its a game you can pick up and pretty much get into straight off.
Part of this game's appeal for me was it reminded me of similar RPG game Severance: Blade of Darkness, which was fairly similar in terms of its combat (and gore). But Dark Messiah of course stands out a bit more as adds so many features in terms of your player's upgrade capabilities. The magic powers and combat system are pretty good, although I admit most of the combat attacks feel kind of the same.
The graphics and presentation of the game are also very good, with really nice graphics and character models look not too bad although they are a little crude in places. The audio for game is great too, the music score is really well done and one of the best I've heard in ages for an RPG. My only criticism of the audio though would be some of the voices which feature guards speaking in American accents going "Hey pal!" and "Where are you going, buddy?" and this is supposed to be a period setting game!
But these are very minor quibbles as Dark Messiah is really good in my opinion and as far as I'm concerned it is far more entertaining and accessible than the overrated Elders of the Scrolls: Oblivion, which I personally couldn't get into at all.
Also I heard this game is supposed to have a number of bugs and issues, but if you patch up to the latest version you should be fine. Dark Messiah is a great game, buy it!