There's something stuck in my gums send help >>51
Cool, I could do 600WPM with the sample they have.
The main problem is if you want to read something where you can expect to run into unfamiliar words often, since you won't really have the time to look them up, or memorize how they're spelled depending on how fast the text is going, but I guess you could just pause if you really cared.
There's a website that provides a similar service for free called spreeder. It only shows you one word at a time without concern for its placement other than centering the word, and I find I can get up to 700wpm and still understand the sample text. It also allows you to paste in your own text.
Something that could be really interesting is a textboard designed with this sort of thing in mind. All of the posts would have a "play" button in the body. Too bad I don't know enough to do that.