YES!!!! My Number 1 Gmail wishlist item has been fullfilled! I can now use Gmail for all emails! Even corporate mails!
Why? Because I can now use Gmail to compose and send out mails using my other email addresses! So, once I get all emails to firstname.lastname@example.org to be forwarded to my gmail.. I can send and receive them inside Gmail itself!! Now I can stop running yet-another memory-hogging email app and get reeeeeal good email search. Thunderbird was my sweet escape from Outlook.... but Gmail takes up less RAM ;-D
Wayyyyyy sweet :-D and yah, this is much sweeter news than Google Talk itself, sadly.
Update: Er... a wish on top of this wish, can the signatures the tagged to each outgoing email as well?
Update: for the concerned, the gmail headers Return-Path: and Sender: states your gmail address.. Received: header indicates its been thru wproxy.gmail.com server.. Message-ID: carries @mail.gmail.com. Other end-user usage experience is smooth. i.e Those headers aren't normally displayed, and recipients can hit "Reply" normally, etc.