I'm using the FLOSS version of Zimbra 5.0.16 and CalDAV-ing into it with Thunderbird 3.1 and Lightning 1.0b2. In general, it is working splendidly.
The one exception, is this: At times, the CalDAV calendars will not display their appointments in all of the views. IE: The entries will only show up in the Day, Week, and Month views. They will not show in the Multiweek view.
There is little consistency I have been able to nail down. The "broken" view(s) are not consistent, at times all of the views work.
The calendars are on the large side: some have a few thousand entries.
Is anyone using the new version of Lighting? Success? Is anyone seeing these symptoms?