[MetalMilitia]

I have an O2 XDA2. I guess it's more of a smartphone than a traditional PDA but it runs Windows Mobile so it does everything any other PocketPC can do.

PocketPC is a platform, much like PC or Mac. That means provided you have a decent enough processor in your device you can run any PocketPC software, i.e. You can probably get Doom and Quake for any PocketPC.
The PDA you mentioned looks more like a really small laptop running, like, Windows 2K or something. Not sure how useful it would be to be honest. Much like the new UMPC form factor it doesn't seem to be good for anything in particular. You may as well either get a ultra mobile notbook (Samsung Q30 or similar) which would be slighly larger but have far better functionality or a PocketPC which would be way smaller and do most of the important functions of the Jornada 720 (surfing the net, sending e-mails, writing notes, viewing appointments etc).