I’d like to present you with Lightning 1.0rc2. You can find it at its new location on the addons.mozilla.org beta channel (If you still get 1.0rc1, then please try again in a few hours when the page cache has been updated).
There is a big new feature in this release which needs your testing. Thanks to the hard work of Mohit, who has joined us through the recent Google Summer of Code, we have extended the cache with full offline support, which means you can write your events while in offline mode. If you are using a CalDAV calendar, it will even retry events that failed.
If you encounter any issues, please file a bug at bugzilla.mozilla.org.
Note, if you are using the cache with the Provider for Google Calendar, please stay tuned. I will soon post a development version of the provider containing a patch that corrects offline support.