I personally like the game, but there are some things you need to get used to when you play.
1. Controls: they are not the standard button layout. Once you spend about 10 min with it, you understand why and appreciate the fact it's different (good reasons)
2. Initial inventory (and some would argue inventory limits through the game). If you're used to having a 'gob' of weapons, ammo and resources, you'll need to get used to the new and slimmed down offerings and be careful what you use and when.
3. Darkness and contrast: The game has no built in (last I played, if there's an update, I'm both not aware of one, nor have I played with a patch) controls for darkness and contrast, meaning you'll have to adjust your TV for this ONE game. If you have presets you can custom make and load on the fly, then this may be a small issue for you. For me, it's a pain in the butt, I can either adjust it and play Thief comfortably, and then adjust back for everything else, or I can suffer with an overly dark, almost muddy viewing experience. (my TV is from 2008, so it very well could be too that the ratios on it aren't vast enough to accomplish this without messing with settings.)
Other than those 3 things, the game play and story (for me) is really good and fun to play.