Actually, it is pretty cool. Though it works better if the 'shape' of the word is close, i.e. letters without ascenders or descenders are out of place, rather than ascenders or descenders in different plaes than they usually would be. That's why istlef isn't immediately obvious as itself., as there's a dip in the center of the correct spelling, while there are two dips in istlef. ilsetf seems to be easier to decipher.
I can read most words when the letters are cut in half or worse, and extremely blurry type. I can read upside down and backwards, but without my glasses, I can't read anything more than six inches away. :p