Well the Psion 5MX is a great step up form the 3 or 3c. But even that is looking dated now as it has no colour screen and no posibility of bluetooth or WiFi access.
Depending on what you need to use it for the 5MX could be the way to go but it is an end of life product, supported as far as spares go but not being made anymore.
The Psion Netbook is very nice, still a live product, colour screen, WiFi access etc. however it will not fit in your pocket!
Pretty much anything else in the market is stylus based (optional add on or on screen keyboards).