PocketPC 2002 by MS might look nice, might be nice, but PalmOS not only has a very large installed user base (80%+), it's also still selling more Palms than the PocketPC competition together. Plus there's Sony, Handspring and others doing quite well.
PalmOS 5 actually sounds quite promising. They're taking the GOOD stuff of Palm and add the GOOD stuff that needs to be added. We'll see when the devices are out, though.
Plus, there is Mac compatibility out of the box.
The REAL competition for Palm & PocketPC is Nokia with its Communicator 9210i (9290 if you live in the US). Somehow, communication comes second @ Palm & PocketPC, while Nokia, of course, is first a communications company and second a PDA one. Take a GOOD look at the Communicator before judging other PDAs which don't offer you good integration between different communication methods.