I yesterday bought a palm m500 and found out it is working with no problems at all with my Entourage PIM. I installed the newest Palm-Desktop for OS X, then installed the Microsoft Handheld Sync Conduits (you can get that at mactopia) and it really works great. Pushing the Sync-Button on my docking-station and the sync of all my entourage-data started and synced my m500. Working in both ways plus softwareupload works two. Great.
Btw: Works on X.2.1
Btw: Works on X.2.1