I just acquired a
Sharp PC-Z1 Netwalker.
For those who don't know, it's the second coming of the Sharp Zaurus.
Form factor is similar to those nifty pocket dictionaries/translation tools that are so big in Japan, only with a colour screen (1024x600) and an ARM Cortex A8 clocked at 800MHz running Ubuntu 9.04. (RAM: 512Mb. Storage: 4Gb FLASH SSD, plus microSDHC slot -- mine's occupied by a 16Gb card -- and two USB ports. Wifi, no bluetooth.)
I can confirm that FBReader is installable via "Add/Remove applications" (i.e. nearly idiot-proof). There's an outdated version of Calibre in the Ubuntu repository; I'm going to try building 0.6.14 later today (it needs some dependencies fixing first).
The screen is pin-sharp and very bright, and while the official battery life of 10 hours is unlikely, reports of 7.5 hours with wifi are probably true. The real attraction is a pocket netbook that can run OpenOffice, Thunderbird, or Firefox ... but it's promising enough as an ebook reader to be worth a look.
(Grey market imports available via conics.net; mine came from a different source, although I've bought from Conics before and my experience of them was good.)