Just got my hands on it from Humble update.
So, Level 1 - no change, it seems
Level 2 - massive update, a lot of new stuff added, new street, limited access to roofs, new "bladerunner" sidequest, optional bank robbery sublevel, wrestling arena. Its full of fresh meat!
Level 3 (resort) - small amount of stuff added, like "dimentional sliders and travel between paralled dimentions", funny but nothing really special.
Level 4 - nothing changed.
Wedding Quake - massive update, 4 new big maps added, based on main game levels, a lot of new weapons, multiplayer. Bots is as still with huge advantage as before and most of ranged weapons is crap.
Sad thing is that they didnt added new levels, probably decided to save it for DLC. News stuff is good but game is still rather short.