I'm glad I didn't buy anything I mentioned in my roundup of App.net clients because Tapbots just released Netbot - a version of their popular Tweetbot Twitter client for App.net. And they've added one big feature that a lot of App.net folks are trying to sort out - how to crosspost to Twitter:
Still have friends on Twitter? You can use Netbot to crosspost your Posts to Twitter. You can also use the search tab to see which of your Twitter friends are already on App.net.
They've released an iPhone and iPad version: Netbot for iPhone - $4.99 in the App Store and Netbot for iPad - $4.99 in the App Store.