I don't mind the petstore, I don't mind the mountstore.
I don't mind paying if something pops up there that I think is really nice, although I am a little sad it's not available for regular play.
I DO mind the neverending stream of utter crap everyone in the game feels they are entitled to give you the second you show up on one of those mounts.
I play on an RP Server. I /had/ a character like Johnny Awesome before it was done in the horde questline who thought his sparkly pony was just fabulous. Right up until the moment I started gettig kicked from pugs just for having the thing...
I would've liked it a lot better if there was some kind of in-game way of getting these mounts, but then there'd be another schism between people who got it in store (slackers!) versus those who earned it in the game (no-lifers! booo-urns!)...