Not sure if you were looking for information on the handhelds themselves or the performance in a wireless environment. I dont know much about the handhelds but the type of access network will seriously effect your views on performance. In a GSM/TDMA network, because they are 'circuit-switched', i.e. you have a permenant one-to-one connection, continuity can be quite a problem, especially if you are mobile in anyway. Future networks should (will) see a vast improvement as will use packet access, just like the internet. In Europe these access methods are GPRS and shortly, UMTS. I'm not sure what they are in the USA. cdma2000 is the amrican equivalent of UMTS I think, and I know there is a GPRS-like network for cdma-95.
In summary, I would wait if thats possible, until these 3rd generation networks become more available.
"A problem worthy of attack, proves its worth by fighting back" - Paul Erdős