Other than several memory cards (or a suitable hard drive), a (small) keyboard will be a must for me, as I intend to use it both for programming and everyday LaTeX procesing when a normal computer isn't accessible. Maily because the backslash and curly braces will be used so often, and they seem to be in quite inconvenient places on the unit.
That's about all I plan on getting though, as in its current state (in general, not just on the pandora) bluetooth sh*ts all over the quality of any audio, and I already have an audiophile-quality mp3 player, and everythign else I plan on doing with it can be accomplised through USB or WiFi.