NotePad++ has numerous advantages over Crimson Editor, including an autosave, which it lacks, but one thing I miss about it, is that its spellchecker can underline words in red when they are misspelled. That way, if, e.g. there are parts of text files, such as HTML headers, that you know will have a number of errors, you can just ignore them. Of course, it is very helpful that you can have Notepad++ just check a highlighted section of a file. The other reason it is very helpful to have the underline style spelling errors is that you are not left with a ton of errors at the end, and you can improve your ability to spell with instant feedback, so there will be fewer errors to check, ultimately. By the time you get around to spell-checking a document, you may be zipping through corrections so fast, you might not realize the context for the correct usage of the word, and then, suppose you choose the wrong correction. You have to try to find it again, and now, it is no longer misspelled. This all goes away with underlined spelling errors.
MS Word, Open Office Writer, FireFox and eclipse, among others now support this feature. I do like the usage of aspell, however. It differentiates between U.S. English and British, whereas many other dictionaries do not; it gets more conjugations, and has a really small dictionary size. I suppose since the spell-checker is a plugin, this will either need to become a part of Notepad++ proper, or else have the plugin architecture modified to deal with the little red spelling underlines.