Federico has the news:
To my surprise, the app – which was pulled from the App Store after the acquisition – has been updated to version 3.0 this week, adding iOS 7 compatibility and fixes. There are no new notable additions, but the entire Poster UI has been updated for iOS 7 and there is a new line height option in the preview menu; Witkin got rid of textures and iOS 6-style buttons, adding subtle animations for navigation and other menus. It's still the same Poster, only with an iOS 7 interface and less crashes.
However, the bad news is that, because the app isn't available on the App Store anymore, only old customers can download the updated version. If you bought Poster in the past, open the App Store, find the Purchased section, and look for Poster; tap Open/Download, and the app should be reinstalled with the new version 3.0 that Witkin made for iOS 7.
Talk about a cool, unexpected, surprise.