Never used it.
Like the idea of it, but its been a bit of a fail.
If developers bothered to use it, it could be good, but everyone seems to be trying to create their own multiplayer standard by using other methods.
Everytime I download a new app, if I want to use multiplayer I have to sign up for new crap service.
It needs more apps.
And as for tracking achievements, maybe because I didn't grow up with them, but they mean nothing to me.
I think its possibly something kids try to achieve on games these days, but why anyone cares about them is lost on me.
