I've been playing the game at first @ 1024*768 w/ 2x multisampling, and my fps would go down in to teens a lot of the times(usually when looking at those big blue fires, or when enemies have torches). I tried 12*10 w/o multisampling or bloom, and my fps was even worse. I kept playing @ the settings I mentioned first, until 3 days ago, when I changed it to 12*10 w/ bloom on. My fps is much better for some reason, and the game looks better, without "noticeable" jaggies(on a 19" monitor).
From my experience w/ the game(7-8 hours into it), I have to say that it's almost as good as thief 2. I just wish the levels weren't small w/ loading areas, and you could go on rooftops.