I'm interested in the possibility of programming on the unit itself. The low-power consumption makes you less dependent on mains power.
EDIT according to http://www.mobileread.com/forums/showthread.php?t=95968, it's an iMX35 (ARM11-based) http://www.freescale.com/webapp/sps/site/overview.jsp?code=I... (probably iMX353 or iMX357: max speed... 532 MHz)