The biggest beef I have with PS3 online is the fact that there isn't a large number of people using headsets. I can deal with the occasional racist prick yelling at his mom for some chocolate milk, but I can't stand silence or a single voice yelling "does anyone have a headset" in PS3 online games. Also the only online community I've hated is Halo 2/3, Gears was fine and so was COD4's in the beta.
I love how huge Sony fans can just gloss over this by saying "less racist 10y/o", the problem lies in that there is very few people with headsets period, as a result you can't even talk to the normal people out there. And for shooters that work best with some for of communication (especially for the objective gametypes), this is a major negative for the platform. I still wish Sony would bundle in a cheap headset with the PS3 like MS did with X360 Prem/Elite. The best way to encourage a solid community aspect is to make sure people can talk to each other, even if sometimes the other person is an idiot.
Lack of integrated friends list, messaging and invites adds to the problem too.