I think Blind_Prophet's talking about Thief 3, a.k.a. Thief: Deadly Shadows, which came out last June for PC.
I'm a huge fan -- the graphics are just drop-dead gorgeous, and the AI has gotten so good it's freakish.
http://www.thief-thecircle.com/thief3/danspreview.asp
Check out Digital Nightfall's review above, it covers just about everything. Of note is the weird 1st person movement (a la Arx Fatalis, which I also love).
I say get it! I've never quite gotten over the novelty of the first Thief game, but I think (objectively) they've gotten better with each addition to the family.