An update to Rocket Chimp is nearly ready to be submitted. This update will be more of a technical update, including many new iOS 5 features. It will add iCloud support for syncing high scores and achievements between your devices. Also it will use the new Twitter integration to make tweeting much easier, no longer requiring you to log-in inside of the app.
Also, instead of getting it ad-free for two weeks you can now get the game completely free just by tweeting the #rocketchimp hashtag from inside the app! This update should be coming no later than next week.