I wrote a script to do that:
Thing is, once you start throwing lots of more robust text in there (excerpt from a book, etc), it becomes very apparent that it really only works with simple, common words. Once you start using proper nouns and more diverse vocabulary, it becomes very difficult to read the scrambled text. Also, the way the words are scrambled makes a big difference too. I ran your text through my scrambler a few times, and some of the results were harder to read than others.
Here's the summary scrambled, and there are parts that can be read pretty easily, but then there are words that simply can't be read "automatically" and you have to sit and think about them.
Meiahcl S. Rlwosnead rtoreps in the Wnasitgohn Psot taht, adrnioccg to covniitge ntesenucoiirtss, haumns seem to be dopnvileeg daigtil binras wtih new crtiuics for simnkimg torhguh the trneort of irfianoomtn oinlne at the eespnxe of taadinrtiol deep ridneag ctucirriy... Mraaynne Wlof, one of the wlrod's fsmoroet exptres on the stduy of rnadieg, was stretlad last yaer to divseocr her bairn was aertpnalpy antiadpg, too. After a day of srincollg tghoruh the Web and hdedruns of e-malis, she sat dwon one enenvig to raed Hearmnn Hsese's ciannlhgleg nvoel The Galss Baed Gmae. 'I'm not kniddig: I cdluon't do it,' syas Wlof. 'It was troture getitng touhgrh the fisrt page. I cdouln't fcroe msyelf to solw down so taht I wsan't siknmmig, pciinkg out key wdors, ognranizig my eye moetvnems to geantere the most ifianotromn at the hsiehgt seped. I was so digsutsed wtih mylesf.'
The bairn was not dseengid for riaendg and trhee are no geens for radenig lkie three are for lauaggne or vioisn. ... Bfeore the Irntneet, the barin raed mtlosy in leianr wyas — one pgae led to the nxet pgae, and so on. The Inntreet is deneiffrt. With so mcuh iorfainomtn, hpyernilked txet, vedois asldgonie wdors and ireittntavciy eewvhrerye, our branis form suothcrts to dael wtih it all — snnicang, sinhcaerg for key wdros, srlclnoig up and down qilkcuy. Tihs is naneoilnr rnieadg, and it has been dmteucnoed in amcadiec sduetis. ... Some rseahrcrees bilveee taht for mnay polepe, tihs sytle of rneaidg is bnngiieng to idnave our abiltiy to dael wtih otehr mdeuims. 'We're seinpndg so mcuh tmie tincohug, psuinhg, liinnkg, sinlolcrg and junipmg toughrh txet taht wehn we sit dwon wtih a nveol, yuor daliy hbatis of jpmuing, ccilnikg, lniikng is jsut iareingnd in you,' syas Anerdw Dloiln."