I've owned pretty much every PDA there is. And none of them come close to what a nice small notebook can do for you. Granted; technology has improved, and some PDA's can be tricked out with Bluetooth keyboards, a mouse, VGA out, modems etc... but at the end of the day the operating systems and software simply do not make them practical alternatives for real life applications. For a one or two day trip you might be ok, but even a simple task like sending an email on a PDA can be a nightmare.

If I were you I'd look into a sub-notebook or perhaps even a micro notebook like an OQO or Toshiba Libretto.