I've only used a few portable devices, though the time span is rather long:
- HP LX320 (Win CE 1.0 and later v2.0)
- Fujitsu B112 (Win98 sub-notebook w/ touch screen)
- Sony Clie 415
- Sony Clie UX50
- Kindle 3 - still my current device
I used various PCs, including one notebook, to read ebooks for several year prior to getting the HP palmtop device, but their use was not primarily as a reading device.