Last year, I started using Posterous, both as blogger and developer.

As a blogger it worked fine.

As a developer it was terribly supported. The API was fine, but the implementations were often terribly flawed. Tags could not be deleted. Posts entered with markup could not be retrieved as markup. It was almost impossible to connect to an engineer at Posterous who cared.

I do hope Posthaven succeeds. I encourage you to have an API. I encourage you to treat your external developers with the respect Posterous was unable to show.