I've seen a lot of proposals for additional input device suport. As an electonics engineer, I'd love to see tihs and be able to have custom input devices.
Ona a similar note, my suggestion is to extend the value of llTakeControls to take input from several more keys. This would be especially helpful for game developers (You know that thing that SL is supposed to be tailor made for). The ability to define hotkeys, instead of using extra prims/script to add buttons, or listens (shrieks) would be a monster improvement in my book.