Well, here is my experience with the subject.
I tried switching to WM2003 a couple of days ago. Had to perform some tricks but I expected that, so no trouble there.
The troubles started when I finally got my hands onto this thing. Should I say I had the worst feeling about the change of OS. Although I knew beforehand that some programs that I use are not compatible with WM2003, I wouldn't expect that the software that comes as a part of OS will not work as it should be. WMP will play MP3 with loathsome quality. Every attempt to change the volume will be followed by a delay. At high volume the quality will be absolutely unbearable.
Next, WM2003 likes to take up as much memory as it can get. On PPC2002 I had 11.9 megs free (Axim Basic) AFTER loading all my programs, such as IcBar, Total Commander and ShutDown. Now I had only 9.x megs after clean reboot.
I didn't notice any speed improvement. In fact some tasks were running subjectively slower (don't have anything to prove it).

I switched back to PPC2002 and don't want any more updates.

If you understand what you're doing, you ain't learning anything.

I had a similar experience. I have a 400MHz X5 with the older 250 CPU chip. PC2003 ran sluggish compared to PC2002. Apps also seemed to take longer to load up.

I found the "improved" networking setups were OK, but there was nothing wrong with the networking in PC2002.

The new appearance of the calendar and contact displays were nice, but not enough to justify the cons (and cost). You can improve the displays in 2002 with third-party software like Pocket Informant or Agenda Fusion.

I also restored PC2002 and will stay with it on my current Axim.

CM

Amadeus,

You mention a delay with switching volume with WMP is there also a lot of crackling? I remember hearing reports a while back of people complaining of bad audio quality and crackling in WM2003. I was curious to see if that had somehow been resolved since then (although I doubt that).

Yes, crackling is all around (no matter if you use another program while listening or not). Somehow if you play with the volume for a while (up and down) you may make it go away (@ least most of it).

If you understand what you're doing, you ain't learning anything.