We spoke about this at SHDH tonight. My wife and I use Palm Treos and http://www.goosync.com/ with some success. There's one set of events that appears on both palms and a google calendar. My own google account also merges in other google calendars.

I do not have a way to designate that an event on my palm should be on my google cal but not on hers. There are various sync issues every now and then, such as the 'alarm' flag not getting set on events I receive from my wife. In other words, it's really crummy compared to how such a system ought to work, and I don't know why things are this hard. But, it's also a working system that does a useful thing for my personal info, so that's pretty cool.