Rated 4 out of 5 stars

known issues:
- when a calender goes read-only (e.g. only temporarily available via a network) the associated entrys revoke any sort of editing with not clear notice why - i would suggest a read-only symbol for the calenders and for all entrys.
- when looking after plungin details (more...) in the ad-on manager i will see a dangling link like this: http://www.mozilla.org/de/projects/calendar/releases/lightning1.9.html
- when a certain event is assigned a certain color and you are having more than e.g. 10 calenders then the colors do become quite hard to distinguish from each other. this is true especially on LCDs. when selecting a calender entry there is no hint from which calender that entry originates from. e.g. it could be made clear by its name or by highlighting the matching calender by some symbol in the listing.

This review is for a previous version of the add-on (1.9).