The biggest change I've seen has occurred in the past two weeks. I've noticed a rash of riders who choose to track stand at lights, mostly on dork-a-licious fixed gears (I did see one dude in team kit doing it). Maybe these are the fair-weather cyclists that have not seen the road all winter and have forgotten some manners or are just really eager to assert themselves now that it is warm.
Not that track standing at lights is aggressive but it is kind of a pompous show (I find it funny that people think it is some kind of great skill when you can easily pull it off on a geared bike) since it is completely unnecessary, and I don't think I saw a single person do it all winter.