What type of functionality were you looking for? My App makes use of the Apple Bluetooth Keyboard, and I've been testing on iOS 4.2 GM getting ready for the new release.
In general, arrow key support, cut/copy/paste, and movement short-cuts (end of line, end of page, start of line, start of page, next word, etc.) are all application dependent.
If there is a particular App you wish had better keyboard support, let the developer know. If it's an Apple App, visit support.apple.com, search for the App, and make a comment about what you'd like to see.
Hope that helps.