This is great Rated 5 out of 5 stars
Don't listen to some of the other reviews. I have lightning working on both vista and ubuntu machines. It works flawlessly. If you use the provider for google networks addon for this you need to use a nightly build of the gdata (provider) addon found at http://ftp.mozilla.org/pub/mozilla.org/calendar/lightning/nightly/latest-mozilla1.8/windows-xpi/
for it to work until version 0.4 of the provider for google is released.