I've already mentioned it in half a dozen threads, but I'm absolutely stuck on
EditPad Pro. It has all the basic and not-so-basic features you'd expect from a text editor.
Most big text/programming editors have generally the same feature set, the real difference is a matter of subtlety--what you need and/or what you're used to. For me, the real kickers--what keeps me with the same program--is not so much the features but the editor itself. It's text editing engine in general really feels like its first and foremost purpose is text processing -- everything else is gravy. From efficient keyboard navigation to conversion routines to the absolute best regex support on the market. (Regex find/replace features a multi-line text entry area with syntax hilighting, much better than the single <30 char input box most offer) -- and a key thing for me is (optional) persistent selections and inherent add ons to it (ctrl+m to move the selection to your cursor, ctrl+d to duplicate the selected text, etc.).
A few other perks for me -- most of the features are available settings can be stored in an ini file making the application totally portable, there's an application for making custom syntax hilighting schemes (comes in handy for proprietary data formats I use now and again), syntax aware live spelling, external tools -- and whatever else you might think of. The few things that weren't there are implemented in the upcoming version 6 -- whose beta is really stable and sexy, right now

Finally, to my delight, the text processing engine for EditPad is also in JGSoft's other applications--which also integrate into one another in a number of ways, making for a great family of familiar applications--
RegexBuddy,
Power Grep,
AceText -- most of which I use ceaselessly, daily. I feel like a marketeer, at this point . . . I've just been using JGSoft's applications for too long . . .

For quickly previewing text, on the other hand, I usually just use Editor2, which is bundled with xplorer2.
TED Notepad is nice, too. My biggest complaint with minimalist editors -- TED, metapad, editor2 -- they all use the registry to store their settings, which drives me nuts. I like to have the option to drop it on my flash drive and go.