So I did a little poking around into DAISY, and I don't think I'm going to do it. It seems easy enough to convert something into DAISY--there are add-ons for Word and OpenOffice that will save something as a DAISY file--but once you have the file, what then? You can't put it up someplace yourself for people to buy--or if you can, they're keeping that information mighty quiet.
The other thing is that a lot of the things DAISY was designed to do, e-readers can do now. Kindles read books aloud, and apparently Apple devices can make Braille. If you're on Smashwords, someone can buy the .DOC version of your book and convert that into DAISY themselves, and hopefully soon they'll be able to do that with an ePub file. To be honest, I hope that DAISY becomes outdated and unnecessary as e-books become more adaptable.