I'd like an ambidextrous (or even better, left handed) design as mentioned earlier, where there are buttons on both sides and one could swap keymap layouts.

Full size SD card(s) are a must. They store more data at lower prices and greater density.

Faster processor, more RAM.

Peer-to-peer / ad-hoc WiFi file sharing & IM between tablets; Wi-Fi gaming would be even better.

Some kind of gaming capabilities (maybe something derived from the N-Gage failure).

Physical screen lock / standby button (something like the sliding button on the top of the iPod).

Screen that is easily readable in sunlight.