Finding the perfect cross-platform posting plugin for WP is a trip and a half. It’s so much trial and error. I want to cross-post to all the services I use (and there is now a not inconsiderable list) but especially tumblr and posterous. I haven’t been able to import the posts to either service, but one button posting seems to be eluding me.
I am trying out the Publish 2 Ping.fm plugin (as I have had this set up and cocked and used it many times before over the last couple of years) so I’m hoping this will help. News at 11.