My old Psion 3a died of a broken hinge, and I replaced it with an iPaq.
I still reckon the Psion was a better device for what I wanted, but the extra power of the iPaq had it.
The higher-up-the-range iPaqs are excellent - I recently sold my 5555 which was working perfectly but became superfluous because I had one of those do-everything telephones.
I'd suggest that if you liked the Psion, either get it repaired or pick an iPaq.