15 hours in one sitting?! Jesus mate, that's dedication to the cause! :D
I'm up to the first Vegas level which is huge, so I need to set aside a few hours to tackle it properly, although my little brother claims that he did it in a matter of minutes which I find hard to believe.
I thought that the Mardi Gras level was one of the weaker ones to be honest, but it was certainly impressive to have that many characters on screen at once, even if they're only dressed in about 5 different outfits. The rehab clinic I enjoyed immensely though for some reason, probably because I did it perfectly the first time.
Can't wait to see where they take the series next though - a fleshing out of the upgrade system, non-linear mission choice & more opportunities to blend into your environment (leading against the wall pretending to use your phone or tying your shoelaces for example) would be good. Maybe expand the missions out so that they take place over the entire expanse of a town, with a full day & night cycle, rather than the fairly short loops of behaviour that they follow in the present games.
But yeah whatever, Hitman rocks.