It is amazing. I thought all is fine with version 2, but now I see that several things can get a lot better in  thunderbird 3!

@developers: Thanks a lot for this!

1. Search looks very nice, is very very fast and is a pleasure to use. Easy navigating through the result set (is there a search engine under the hood? :-)).
   Here is a screenshot
   
2. Fancy layout
3. Inbox now is by default subdivided into the mailing accounts. no need for virtual folders
4. Tab-Browsing (creating new mails won’t open in a new tab :-()
5. See here for the full feature list!

PS: If you have problems with upgrading

• I lost my master password of the old thunderbird => take a look here (German).
• Only the new 1.0 beta version of lightning works (nightly builds)

Normally the following is not necessary… but for your convenience:

• Email import / export => here
• Calendar import / export => already there (go to the calendar->events+tasks->import or export)
• Addressbook import / export => every list has to exported/imported alone