I just installed Mozilla Thunderbird again after about 2-3 months of not using it. What I found was a more beautiful interface, seemingly faster response, and easier setup (at least for Gmail).
The latest is at 3.0.1 and it's excellent. I believe Thunderbird is reason enough for getting a Gmail account if you don't have one yet. I also believe that if you use e-mails regularly, you should have Gmail as the main service ;') then install Thunderbird to make e-mailing a breeze. What got me into this is the IMAP setup that I think only Gmail implements beautifully.
I almost switched to Outlook as my e-mailing client, but here comes Thunderbird with an improved version. So, congratulations again, you Mozilla people you, and thank you very much!