Having dyslexia, I would say this is rather extreme, I can't speak for everyone but reading isn't like this for most dyslexics.
Usually it is a pair of letters being swapped, or numbers order reversed. They don't jump around/change randomly, you just misread it.
http://dyslexia.learninginfo.org/symptoms.htm
The new font for dyslexics also goes into this some more: http://www.scientificamerican.com/article/new-font-helps-dys...