WM, Stay away from Dell's models. Support has been terrible for the past six months. X50v owners haven't had a firmware update for nearly a year, and Dell refuses to fix Windows Mobile 5 issues they're experiencing. X51v's are also experiencing bad problems with WM5. I'd probably suggest looking at something from HP over Dell at the moment, but I have no idea which model would be the best. I do have some suggestions on looking for a PDA.
What you want to look for in a PDA though is the type of processor, for sure. I'd go with the Intel XScale PXA270, the chip that will allow your PDA to run up to 624MHZ. I steer way clear from the Samsung processors. Be cautious because some of the PXA chips only go up to 416Mhz, check out the specs thoroughly. The other things to have in your PDA which I feel are indespenible are Bluetooth AND WiFi. If they're built in, you don't have to sacrifice a storage slot for that sort of functionality. Then, treat yourself to a TRUE VGA screen, not a QVGA screen. Your eyes will thank you later.
If you have a PDA with that kind of horsepower under the hood, you'll have way more flexibility. Then you can grab a free MP3 player called GSPlayer which basically turns your PDA into an iPod, without the crappy iTunes interface. Just load up the songs on the card, insert, load them up in the player, and bam, you're set. As for scheduling and all, every PDA with Windows Mobile 2003 or 5 will come with the pocket versions of Outlook, Word and Excel. The CD that comes with it will include a version of Outlook for your PC, which you will need to use to make that scheduling data work with Activesync. Activesync is the syncronization software btw.
Here's a couple of tips that's worked for me in the past. If you want to be mobile, and you have a book bag or something that you might carry to class or work, get an extra AC adaptor, with whatever adaptors you'll need to hook it into your PDA. This way, you can plug in your PDA at work if you're at a desk and not drain your battery. Second, DO purchase an extra battery. You won't believe how fast your battery will get sucked down when you start using WiFi. Bluetooth isn't as bad on the power usage, but it still drains it a lot faster than with it off. Third, consider buying an aluminum case for your PDA. RhinoSkin makes some nice cases for most popular brands of PDA out there. Unless you want the leather-executive look, then I'd go with a Sena or Piel Frama case. Aluminum tends to be cheaper though, and it looks cool.
If you have specific questions, I'm sure I can help you out with em. I've been using Windows-Mobile PDA's for about two years now and I'm way more involved with using it for a glorified calendar, so I know quite a bit about em. The Aximsite forums lean toward Dell Axim PDA's but are still a good set of boards to read up on if you want to do a little research. Brighthand forums are more of a catch-all for everyone else, but I think they tend to lean toward the HP brand.
