I really don't see how Pownce was in direct competition with Twitter. On the messaging side there certainly was competition and I can see that Twitter wins that battle, but Twitter doesn't do all the rest very well.
How do I send someone a song over Twitter? Upload it to rapidshare and send them a link, please. I always saw these services as complementary, though I never figured out how to perfectly balance my usage.
Any thoughts on the features that Pownce does better than Twitter?
Any sites that will replace Pownce? Utterli perhaps?