Unless one is so versatile with XHTML as to be able to write pure code down on napkins (or in TextEdit or WordPad), I can't imagine living without BBEdit.

I only wish it's Help files & built-in "tutorial" were better organized & indexed - starting with an alphabetical index built in to the help system. Trying to find solutions to arcane problems can be a real challenge, and some topics significant enough to be menu items aren't even listed in the help files.

That said - this is the heavy fuel of choice for most web coders I know.