I've been a hard core BBEdit user since BBEdit 6 (way back before MacOSX). It's a great text editor, and has many awesome features. I've actually stuck at BBEdit 7, since the Big New Features in BBEdit 8 weren't that big to me, and I couldn't justify allocating budget for the upgrade license.
I've also dabbled with SubEthaEdit, but only seriously as a collaboration tool, never for serious text editing on my own.
However, I was just using it to edit some files, and it's really nice as a standalone editor! It's got just about everything I like about BBEdit, has a great UI, the collaboration stuff, and it's free for non-commercial uses.
The command line tool works nicely (without spewing up extra untitled documents if the app isn't running when a document is opened via the command line tool), and integrates as a standard EDITOR, so I can use it for subversion commit messages. It's got syntax colouring for any language I care about, which is nice.
The only thing I'm left wanting for with SubEthaEdit is code reformating. BBEdit has a great tool for reformatting HTML (and XML), and that's invaluable when writing that. It's also handy to be able to clean up the formatting on a chunk of java code, so the curly brackets all line up nicely so I can follow flow more easily. I suppose a separate reformatting tool would work fine, especially if it's callable from within SubEthaEdit.
I'm going to try switching to SubEthaEdit as my primary editor for a while to see if it works as well as BBEdit in practice. I may even set XCode to open files for editing in SubEthaEdit (although XCode has a nice - but not perfect - code reformatter built in).
Now, if only I could find an efficient, well designed editor like SubEthaEdit, with the powerful code cleaning/formatting of JEdit...
Update: Holy. Crap. Check out the demo movie of "block editing" - this could come in extremely handy!
Update: Well... One day with SEE, and I'm still pretty happy with it. I keep catching my reflexive command+option+shift+f to reformat html, but that's not fatal... Besides, I'm supposed to be off for the week, so I should be spending less time reformatting HTML anyway :-)