Mike you are right...I think all lighting in the game is completely real (no predefined shadows, even those cast by walls, etc.
Personally I play at 640x480 2x "multisampling" (in game setting) with every detail on and it runs about 25fps (fraps) which is more than fast enough for Thief. The thing I don't understand is if I turn all the details down and play at 800x600 it runs much slower, especially in shadow heavy scenes (like through metal bars). I have an Athlon XP 1800 and GF5200 Ultra...do you think its cpu or video limited? (I know, the answer is "both!"
Maybe I'll borrow a 5900 from work and find out.
The only thing I can't stand is the level load times...why couldn't they have loaded the full map into memory on the PC....grrr xbox...
Deus Ex 2 was bad about this too.
But seriously...its a bad game because it doesn't run at 100fps??