Wifi: so I can get to internet and check my online sources for books (such as MobileRead!) and forums (such as MobileRead!) Also, the ability to connect to my server and NAS at home would be very nice indeed.
Touch Screen: I would like to be able to annotate (for correcting) the books I'm reading so I can go back to the source and update it accordingly.
Stylus: Finger is nice, but not accurate enough. I have thick fingers...
Colour screen: a must-have. A 9.7" device would be used a lot for comics by me and thus colour is required.
Web-browser: see Wifi
Document Search: I'll be putting a lot of documents on it, searching through them would be very helpful!
Dictionary: my English isn't perfect, there are still words I don't know and having to look them up at a later date is annoying. I prefer to find them immediately (even when I don't have access to wifi!)
Other (please specify): (I know, it's not there, but still
) not too many buttons on the device (please, no onboard keyboard! they only make a device cumbersome), but a previous/next and menu button would be very handy.