I have a Sony Clie PEG TH55 - a nice device that has everything a business PDA needs. So camera, MP3 player and other gadgets. Oh, and of course it can do calendar and stuff too.
What it can't always do though: play my MP3s. I have various MP3s created with different programs. At first I thought only the 192 kbit MP3s from iTunes were causing trouble, so I quickly converted a bunch of songs from my iTunes to 128 kbit MP3s (using Amadeus II - a really cool audio editing program!). Well, the result: Pink Floyd songs work, those were converted from AAC tracks (I ripped them more recently). Emerson, Lake & Palmer doesn't work - those were 192 kbit MP3s before, but were saved as 128 kbit MP3s the same way. With the same software.
Anyway, my iPod is much nicer and more pleasant for music anyway. I had just hoped to get by with just one device in an emergency, but that's only very limited with the Clie. Annoying.