TERSONO D'oh. you've missed the whole point. Yes, you can use it as a BBEdit replacement if you wish, but it is so much more than that (and I'm speaking as a professional web developer and registered user of BBEdit since version 4).
Coda's strength lies in terms of workflow. Previously I'd have BBEdit (or latterly TextMate), Interarchy, CSSEdit, a finder window, at least one terminal window, Photoshop and Safari open continuously. Even with expose and dual screens, switching between apps becomes a pain in a hurry. Coda allows me to rationalise this down to two apps only; Coda and Photoshop, improving my productivity generally.
(Version 1.0.4)