I routinely test web applications with screen reading software; I am partially sighted so I have an interest in developing things that work well with screenreaders. I highly recommend "being blind" when you test the things you build, and the idea of blindfolding yourself for a day just to see what it's like is a good idea. It gives you a little more empathy. However, please keep in mind that it's also not as bad for the blind, as they have a lot of practice using assistive devices, technology, etc. The human body and mind are incredible, adaptable, wonderful things.

P.S. I did a video of a screenreader and twitter a few days ago - you can see the thread for that at http://news.ycombinator.com/item?id=1799246