I go to multiple cons a year, mostly based around Northern California (where I am, Fanime is where it's at) and have been doing so for what, seven years now? Jeez. I'm a cosplayfag too, and I enjoy shopping the dealers' rooms and going to panels.
I find it quite refreshing to have a weekend where I don't suppress my power level, and (as contrary a concept as this is to /a/) I have a lot of friends that also go to conventions, so I have many many social interactions. Also I end up meeting many people by cosplayfagging from series that I enjoy, since they're all weird/obscure enough that it's an instant ice breaker for anybody who recognizes me.
Yeah, there's the occasional Cat Piss Man, and invariable cosplay drama, but I actually LIKE anime cons.