I'll repeat myself but I'd go for NEdit. It uses the standard keyboard shortcuts (ctrl-x/c/v cut,copy,paste, ctrl-o/s/q Open,Save,quit, etc) and is as expandable as anything else. I've written Perl autocompletion macros for nedit you'll find easily on the nedit wiki.
Vi and emacs are tools worth knowing about, but they enforce whole new paradigms and shortcuts (they're available for windows, too).