I'm one of a very small number of people who use Palm Desktop 4.1
(only available with T|E and T3, supports Date Book/Calendar
categories) on both Mac OS X and Windows. So I can pass on something
that may come as a bit of a surprise.
There's no comparison between the two applications, which look nothing
alike. Desktop/Mac is far superior to Desktop/Windows. One minor
example -- there's no way to export all appointments from
Desktop/Windows, in Desktop/Mac you have 3 export formats, as well as import
and "merge". On Desktop/Win you have a few paltry task filters, on
Desktop/Mac there are filters and views galore.
Turns out the Palm Desktop/Mac started life as Claris Organizer - a well regarded second generation Macintosh PIM from the 1990s. 3Com (just after US Robotics days, before Palm) bought it and created conduits for it. It's a pleasure to use compared to the clunky Windows Desktop app.