I’ve been waiting for this feature for years and finally it arrived! For those of us who have multiple accounts configured in Gmail, custom per-account signatures are supported. No more copy-pasting from templates, Greasemonkey scripts, and Canned responses trickery. Go to your Settings and configure a separate signature for each account. And it gets better than that – you can even do rich-text signatures if you use HTML emails a lot.
Thank you! Thank you! Thank you to the whole Gmail team and those guys who made this handy feature happen. I wanted this for a while!