-Voice recognition, ala Newton, except that actually works
-Easy to develop for, ala current PalmOS
-Truly multitasking, ala Windows Mobile
-Cross-platform sync ability, ala current PalmOS
-Cell phone, 802.11, bluetooth.
-And thus a web browser, ssh client, and maybe a good mail client
-Reasonable media player, so I can use it in lieu of an iPod (and preferably a good enough interface that I'd be happy to do so). Bonus points for streaming.