One of the most popular articles on this site is Remote controlling Keynote for iOS via Bluetooth, which contains a step-be-step description on how to establish a Bluetooth connection between Keynote for iOS (e.g. on an iPad) and the Keynote Remote app (e.g. on an iPhone or iPod Touch). The problem with this article is - that it only worked with iOS 4.x and that Apple broke the Bluetooth connectivity outlined in that article with the iOS 5 update (and iOS 5.0.1 didn't fix it).
Well, the good news is: The just-released iOS 5.1 fixes the problem. You can now establish a Bluetooth connection between Keynote and Keynote Remote (for iOS) again. Hooray!
Note: The WiFi connectivity wasn't affected from the problem.