Doing PDA functions properly on a general purpose OS, as opposed to a dedicated
singletasking real time OS, is actually quite difficult.
When you switch to the palm datebook, it knows you weren't just looking at it,
and so it brings up today. GPE can't do that. If you're not paying attention,
you'll put your new appointment on the wrong day.

All of the programs are running, there's no load time. Response is instant.
There's no saving of files, because you're working on live data in RAM.

It's an entirely different paradigm.