Matt chooses Groupcal; limits of Plaxo

Matthew Mullenweg, creator of WordPress, has also been looking for calendar interoperability. He settled on Groupcal. Groupcal won't do it for me because it requires an Exchange server. I want Exchange-free synching between Outlook and iCal. Plaxo got mentioned too in his comments. But Plaxo apparently only syncs Outlook client to Outlook client. While that may eliminate the need to have Exchange to share Outlook calendars, I didn't like Plaxo's privacy policies when I looked at them a while back; I recall getting spammed by Plaxo when I responded to someone's request to update my contact info in their Plaxo account.