Its usually not as simple as booting off of the USB, having come from another ARM processor based PDA to the Scroll tablet, there was a lot of work needed before Ubuntu would run on it. There is a site omegamoon which shows what is possible with Ubuntu on a PDA, I've just got in contact with the guy who did the conversion to see if he's interested in Ubuntu for ARM Tablets.
Scroll:- Android 2.1 firmware 1.02 with keyboard.
Done:- Rooted, ReProfiled, DePhoned, Chinese support, Youtube, Market, Printing
To Do:- WIFI Tethering (via phone), 3G Dongle (via usb)