I’ve been running the iOS 5 beta’s since late July and have not seen any major problems in all that time, so I think you’re unlikely to have any problems. Of course, please let me know if you do see anything untoward.
Having said that, Yummy does not have any iOS 5 exclusive features. It still uses its inbuilt Twitter client rather than the one built into iOS; there’s no iCloud support or any of the other nice and shiny new stuff.
