Well, you can try using whatever editor you like; some GUI editors will have session-related issues from running root, and won't work; if you can't get your favorite, go with your favorite screen editor (I use JOE (with stylus support) for almost all editing on the N800), or maybe even sed...

(Sorry if the non-specificity is annoying, but while all the respondents so far are probably arrogant enough to tell you which editor is best , I think none are sufficiently presumptious to tell you which to use. If you want to use that piece-of-<insert rival editor>, I'm not gonna stop you...)