At about 4 AM EST this morning, Pownce can out of closed beta and opened their messaging platform to the public.
TechCrunch had the preview here.
and .... I'm messing around with it here this week, time permitting, here .
We'll see how this one goes. Best of luck to the 'founders' !
Update : Leah Culver posted this article showing what's all new with the public release of Pownce.