From playing with (and using) technology, especially an iPad and such, I've come to see the genius of plain text files (the ones that end in .txt). They are not perfect, as they have no formatting, which is a bit hard with titles that need to be italicized. If you need footnotes, plain text is not for you. What you gain with this filetype, though, is speed, compatibility, and future proofing (well, as future proofed as you can get).
The move to plain text format seems to have begun largely around the iPhone and iPad, and their problems with syncing quickly and wirelessly. Apple's poorly thought out problems of syncing via cables (who wants THAT when you have these wonderfully mobile devices?) led to creations like SimpleNote. With Dropbox becoming ubiquitous in iOS devices, the circle became complete. You could edit the same file wherever and whenever you wanted, bringing a really new implementation of mobile computing.
For things like bits of research, oral papers, outlines, ideas, TXT is ideal. It can be opened and used in nearly every text editor ever made. You don't have to go and transition old files, as I recently had to do with some old seminary papers in Word 5.0, a version no longer supported in the current version of Office for the Mac (a problem known as data rot). There is very little chance of data corruption, since plain text files have none of the arcane layout and information that Word and other such word processors and text layout applications fo. Files open instantly for manipulation. When paired with cloud storage and syncing ( such as the oh so wonderful dropbox, http://www.dropbox.com), you have files that can be edited from an iPhone, iPad, laptop, or someone else's desktop.
So for notes on projects I'm working on, ideas I'm sketching, lists (such as possible blog topics or books to research), gift ideas for family members, plain text is the way to go. It's even the name of my favorite iOS text editor, Plain Text.
For academics, the challenge is the necessary formatting for italicized titles and footnotes. The best options are doing inline footnotes (which you be doing already with a bibliography manager like Endnote or Bookends) and special formatting (Markdown, a simplified code that can be converted to styled text) that enable a final step of processing. So for drafts, notes, or oral papers, use plain text; for final work, submissions, and so on, pull the text into an editor, clean it up, and spit out a .DOC or .PDF.
It's like a computer library catalogue, as opposed to the old card catalogues that I remember. Sure, there are limitations to a computer catalogue, but the benefits far outweigh the frustrations. The same can be said for dear or TXT.