Aoccdrnig to rscheearch at an Elingsh uinervtisy, it deosn't mttaer in waht oredr the ltteers in a wrod are, the olny iprmoatnt tihng is taht the frist and lsat ltteer are in the rghit pclae. The rset can be a toatl mses and you can sitll raed it wouthit a porbelm. Tihs is bcuseae we do not raed ervey lteter by it slef but the wrod as a wlohe.
(Some comments added that readability is improved if you keep together small morphemes [such as word-final -ed]. And separating digraphs such as sh would probably also make things more difficult. But I was still surprised how fluently I could read that text.)
Edit: See also jwz's entry and the comments on that.