Not perfect, but not as bad as the GameSpot review claims!
Environment
The game looks great on my modest computer and the outdoor environments are pretty well done. Admittedly, the indoor dark areas are a bit samey, but this seems to be standard FPS fare - we all seem to need our dark corridors. But temples and cliffsides and city walls all looked nice and impressive.
AI
Sometimes it can be a ltitle lacking. The fact that the spawn and trigger points can be pretty obvious sometimes doesn't help. But you never feel like you're truly battling against endless hordes of monsters. They trickle along in numbers just low enough that you can dispatch them all easily. The poison spiders are just frustrating, because they mean you pretty much have to train the healing spell or you simply can't continue in some areas.
Combat
This is where I love this game. The enemies feel solid. When you smack them with a club or sword, you can see them react. Sometimes the orcs have moments when you think they should attack but don't (like after ripostes or parrys) and sometimes it feels like they attack too much. But on the whole, the combat is pretty good.
Unfortunately, there's just not enough of it. Not enough enemies, and those you find don't take long to take down. It does sometimes feel like they were trying to show off the environmental physics rather than the combat mechanics with the placement of enemies. I think it would have been better if you had to find these spiked walls and flimsy supports yourself, rather than finding a bad guy standing next to them.
The big downfall is that swordsman is pretty much the only way to go. You can't sneak past the spiders, most of the orcs see you before you can get close, and as soon as you hit one with an arrow they run toward you, making an archer sort of useless. And it's not like there are any really good sniping points where you could place yourself as an archer, or spots where you can set up an ambush as a stealth character. You can customise your character, but you are forced to follow pretty much the same advancement path every time because the game is pretty linear.
Overall
I never had any problems with bugs so I can't really talk about that, but it was really the melee combat which kept me playing. The storyline is a little predictable, and you can see both endings by simply saving before the choice at the end, making it a little less dramatic. The story could've been doing with another few hours of play, and the character advancement should have some of the restrictions removed to allow more freedom.
But if you like sword fights and messing around with physics, you can do worse than Dark Messiah. I think a decent mod team could turn this into something absolutely first rate.