i am using ical with zimbra. i configured ical with CalDAV calendar and see two problems:
1. I cannot send or receive attachments.
2. When i send an invite to a outlook 2007 machine, its off by 1 hour. I am in IST time zone (India); so if send an invite for 9 am; outlook 2007 users get it for 8 am. Its fine with outlook 2003 and other clients like thunderbird.