bluefish
So we're left with bluefish an editor which has just recently hit its 1.0 milestone. bluefish, to me, means a HTML editor, perhaps xml too, but mostly HTML. I know it is capable of a lot more, but for me I prefer other tools for different filetypes. I think really this is going to being the smallest section, but we will see what happens.
Note
The upstream authors seem to be happy with referring to it as a HTML editor, most of the literature I can find does just that. If you are looking for another editor for other filetypes you could do a lot worse than bluefish regardless of the apparent focus on HTML.
bluefish, if you don't already know it, is a GTK based editor(and in some cases competent project maintainer). It actually supports quite a few different languages "out of the box" including C, Java and Ruby. You can add your own highlighting rules quite simply, for gnuplot perhaps(hint hint!). There are some basic wizards which are incredibly functional and perhaps most importantly produce syntactically correct output. Regular expression search and replace, and included syntax references for a few filetypes(HTML/PHP/etc). You can call external commands from within bluefish, with a slight twist on the standard quick fix window at the bottom of the screen.
Note
Unfortunately the CSS reference is limited to version 2, although I suppose it is worth saying that support for the newer draft versions doesn't really exist in many browsers so isn't a great loss.
I can't really think of a lot to say about bluefish, which I believe is a good thing. It does exactly what it claims to, and it doesn't create a lot of hassle for you in the process. You tell a file you want XHTML syntax, and if you use the wizards it correctly formats the output using XHTML syntax. You sit over a tag and hit F3 and it pops a context sensitive dialog to edit the tag. Basically it just does what you tell it to without suprises, the way it should be.
The number of times I've almost found myself switching over to bluefish for all types of editing says to me how powerful and yet simple it is, I'm not entirely sure what eventually holds me back. Given a system with less diskspace, where I actually had to worry about installing whole editors for certain files, bluefish would be installed to compliment emacs. I could easily give up the other editors I've talked about here, that in itself is the biggest compliment I can give to bluefish.
Well, if you read this far and think there are any editors I would probably appreciate on the basis of these ramblings drop me a mail. Or if you have any questions about the content feel free to drop me a mail.