If you want a first-party supported solution, go with a Palm. The new Palms run on PalmOS 5, which is a farcry from the OS 3 that's on your Visor. You might like the Tungsten E or the Tungsten T3. They are both great values.
If you think you'd prefer a PocketPC, two good third party solutions are
PocketMac and
MarkSpace MissingSync. I personally use PocketMac 3, as they offer an academic discount and a trial. Here's a
review that compares both.
I purchased a PocketPC about 3 weeks ago, and it works really well with my PowerMac G4. I can sync via WiFi, Bluetooth, and the cradle. It syncs with iCal, Address Book, Entourage, etc.
Take a look at your options and decide. Post if you have any more questions!
