An essential procedure with a PDA is this:
Install the software you need
Verify it all works
Restart the unit
Run the Backup program and make a backup to an SD/CF card (this will be 10MB-50MB according to how much software you have loaded)
and then when the battery is found to be flat (or when something has stopped working for no apparent reason, which can be quite often) you can just restore the backup.
The PDA market is reportedly declining year on year. Perhaps tablets are taking out some of it; they are getting smaller and WinXP is a whole lot more reliable than Pocket/PC. The downside of tablets is that a hard drive stops working at about FL140 (it crashes). The fancy mobile phones will also be taking out a chunk; a decent phone can do everything which a typical exec is doing with a PDA.
A really nice PDA I saw recently is the IMate JasJar. It still uses Pocket/PC so the above comments will apply, but the build quality appears solid, it has a fold-up keyboard, a 640x480 display, and built-in GPRS. If I was getting a PDA again I would get that one.