I'm running GPE also. Though I've only been using it for several days, I've already had alarms repeated, a crash or two, and an instance of the touchpad tapping input being hung. I've now experienced the touchpad hang when not using GPE so it may not be GPE's fault. I've also discovered that jumping to other days in the same month has been painful. I finally figured out that I need the calendar sidebar for that to be usable.

What about Gene Cash's python apps? Has anyone tried them? It appears that his calendar app uses the maemo alarmd instead of its own alarming like GPE. I didn't see any mention of syncing in his feature list, which GPE can theoretically do already. He does support export to iCalendar file which is close enough to a sync for me. See:
http://home.cfl.rr.com/genecash/nokia/