If it's any help - I've tried them all from the newt to the Jornada and I still use a Psion 3a - because of the spreadsheet on which I do C of G, like other people here. Also, it uses standard batteries (newer machines use rechargeables and you can't always get that done, especially in the Arctic) and the database will take any field you throw at it. Apart from the Newt, it's the only one that my data has been rock solid in.
Phil