For those of you who are still waiting on GroupMe (popular texting service) to re-release their app, be prepared to wait for another few days following a tweet published by the company. The app is currently not available on the Marketplace and the company is still working hard to get the re-written app back out in the field.
The above tweet was posted four days ago but still no news for now on availability. The app is being developed from the ground up and should be released (if not being approved by Microsoft right now) shortly. Usually an old version of an app is removed from the Marketplace if the new version is so radically different in code that an update is not possible. The good news is this sounds like the app will offer some new and tantalizing features that many users have been asking for, probably as a result of recently being acquired by Skype (which is owned by Microsoft).
Thanks Karen and Kalet for the info!