I played through some of city 17 yesterday myself. Some of it was interesting, I liked the use of the plane effect from "Dead Air" instead of the giant AT-AT thingy (I don't remember what they are called), and the gauntlet crescendo event was pretty wicked when running up the parking garage where the antlions come out of the ground. The maps were nicely re-skinned with the L4D2 shininess, but there is the one problem: it IS a HL2 map. So, sadly, it was not originally designed to be played like L4D2 and is a bit more linear and doesn't have the puzzles and such like in Episode 1. Oh, also, i found 3 witches in the first level, TWO of which were right next to each other and in front of the safe room...on normal difficulty.