Immensly fun, atmospheric, with a fantastic storyline and universe. Rather challenging with a smart stealth tactic, and really requires the player to be calm, patient (and also load anytime they screw up... which in my case is frequent) and to really listen to where your enemies are (good headphones are a must).
The only thing that personally irritates me a bit is the tedioussness of getting lost, especially in very sprawling areas. However, IMO that makes you feel more like a Thief and in a strange way, makes them game feel more like you're in the shoes of Garret. You're not going in there with knowledge of every nook and cranny, you have to explore, get lost, get lost some more, cry, get lost, reload, start over, get lost again, curse at the screen, and then finally find what you're looking for. It's irritating, but realistic.
I reccomend this to any fan of late 90's games and especially to anyone who likes the stealth genre.