Kevin from palmOne here. Obviously, I?m a little biased toward the Treo and T3 myself. I just wanted to point you towards the Healthcare Solutions pages on palmOne.com. There you?ll find information on compatible medical software and several case studies about how palmOne devices have assisted medical professionals. I hope this information is helpful to you in finding the best handheld for your father.
I have a T3 on which I use Skyscape products from http://www.skyscape.com, but there are a number of other good companies out there. Just Google on "palm medical software". The T3 does not have WiFi, though, so if you want to surf you'll have to use a Bluetooth or cable-connected cell phone.
The main problem with the UX50 is screen size. Although the resolution is good, it's physically a very small screen. Some people really like them, though. You might still be able to get a new one on eBay, but probably not for much longer.