The amazing thing about PalmOS was how it managed performance by simply saving the state of any program when you exited it and resumed the state when you opened it again. There were of course exceptions for background audio playback, but Palm devices never became bogged down with too many open programs like Pocket PCs did.
PalmOS was so much more usable than PocketPC EVER was. PPC was just insanely broken on so many fronts I was ASTONISHED by it when I -- foolishly, as it turns out -- bought a late model HTC in about 2009.
Among other things, you couldn't even use IMAP with the native mail client. I mean, seriously. In 2009.
Indeed. At the time I was a rabid purchaser of PDAs and I wished desperately to get Palm OS with PPC hardware. Probably every color PDA Palm ever built had an LCD that buzzed like an angry hornet. Palm ergonomics were next-level, though. The Lifedrive is probably the best-feeling device of any kind I've held in my hand.
My only venture into WinMo was an ATT/HTC 8525, which was really a nice piece of HARDWARE, but the software use utterly useless.
The best Palm device I ever had was a Treo 650, which I actually ended up using on and off for a long time b/c it worked SO WELL, and the screen wasn't terrible.
(As long as we're talking about interesting hardware: the Danger "HipTop" device was pretty great from a form factor POV, but was hamstrung by lack of real desktop connectivity as I recall.)
On the other hand if I remember correctly, it had a very primitive C programming environment, with memory handles, that had to be locked down before any kind of pointer could be used on them.
They were also damn sexy: http://www.palminfocenter.com/images/TX_front_yahoo_S.jpg