I've been using Palms from the time when they were still branded 3com and I'm very used to it's workings and "quirks". Macs I've been using from much before that! Actually I was an Apple user before I was a Mac user... only some will understand what this means.

In fact, I've never owned a Win PC! (but was forcibly made to use them!)
I've moved away from the Palm operating system several times, but sooner or later always returned. My last Palm before I decided I wanted to try new things was a Tungsten T. My Wife still uses it. I was also tired carrying of 2 devices so I moved to a SE P800 with Symbian. It was a nightmare getting used to it, and I don't think I ever did, although I used it daily for at least a year. Then the P900 came out, I sold my P800 and bought a Sony Clie TH450 (or something of the sort...) and a normal small SE phone. Back to 2 devices.
Eventually got tired again of carrying 2 gadgets and bought a Qtek s100 (or imate jam or magician or something like that... the small one.) Getting used to it was a pita, but was easier in great part due to Missing Sync for Win Mobile. It worked really well and the small bugs I found were ironed out in the 2 months since it's release. Quickly I found that I had to keep the qtek pretty empty of programs for it to run well. I had to perform a soft (warm) reset once a day and a hard one at least once a month. BIG PITA!

: One of the biggest problems was instaling apps because 95% percent of them come as .exe which made me go through VirtualPC to get working. Errors wre as cryptic on it as they are on Windows ("unknow error"), but the Palm is pretty dodgy in that field too. Anyway, had this for a while and I was really starting to get used to it when the Treo 650 really caught my attention. Bought it from e-bay recently. I think it's a decision I should have made long ago and should have done it when the 600 came out.
Coming back to the Palm system is like coming home for me. It's a MUCH better system and much more stable. All this rambling just to say that I think I'd rather keep an old Treo with Palm OS than buy the latest bell's and whistles with Win Mobile... I doubt I'll voluntarily move back to Win Mobile or Symbian. I'd rather go back to 2 devices.