pownce is like a more organized version of twitter but without the IM/mobile side of it (at least for now). You post notes, links, events and files. all those can have replies (no threading for discussions) and ratings. you can RSVP to events, you can automatically play some files, etc. from a tech standpoint alone it is definitely more interesting than twitter. however, from the adoption standpoint, who knows what will happen and really, that's the only thing that matters. if your friends don't use pownce, you get nothing from using it no matter how many features they add.

PM me your email, i'll send you an invite.