Good, plain, TeX editor

I would suggest you go with Notepad++ (http://notepad-plus-plus.org/)

It is light, free (libre and gratis) and you can have it portable as well (you can run it from a pen drive, you don't need to install it).

It has highlighting for TeX and many other languages, and it is easy configurable. Some plugins are really useful (like the one for comparing files) and I love the capability to search between several documents.

You should really give it a try.

I have recently started using Code Browser http://tibleiz.net/code-browser/ which is excellent. Has the best code folding model I have found. Great configurable syntax highlighting for TEX.

It is missing some features of some other mentioned text editors (for examnple the macro language is a little rudimentary) - but the folding in particular, and a few other neat things has projected it to the top of my list regardless.