Mozilla Thunderbird and now the Lightning Project Calendar - any users?

Anyone out there using Mozilla thunderbird as an email client? (see http://www.mozilla.com/thunderbird/) . I think I may install this on my laptop and have some fun, especially since there's word of a new redesign of the calendar component that looks pretty slick. The redesign is billed as The Lightning Project. More on this at http://www.mozilla.org/projects/calendar/lightning.html