I have a PPC-6800 and I use Syncmate to sync my phone, calendar, etc with my macbook.
Problem is, I've found Syncmate and the Missing Sync both very iffy about connecting via USB. I have a MobileMe account for my business, but it's be great if it worked with my PPC.
I contacted apple and they basically said:
"Teri H (apple support): Basically, the more 'votes" something gets, the higher chance it will be worked on. So get your friends and family to add this idea on the feedback page."
So if you're interested in the MobileMe service, just click the link below and briefly say that you want to be able to sync with your PPC...
http://www.apple.com/feedback/mobileme.html
Now get out and vote!