I'm thinking of buying a used, retro, old school pocket PDA device (or something similar such as a palmtop device for example) for general, everyday use. How do the different types of pocket PDA and palmtop devices differ from one another and how usable are they, one from another? I'm looking at the following types:
(possibly an old, used smart phone with Replicant Operating System installed)
Palmtop style devices like - Hewlett Packard, Jornada, Sony VAIO "P" palmtop-like device, Lenovo palmtop-like device, PSION Series 5mx, etc.
Are there any others I should consider in my search?