Coupled with Santar's thread, I thought it'd be fun to see what people can do on this. There aren't results, because it can't predict how many words you retained, but it's pretty clear when you're doing well and when you're not. Basically start at 300WPM or so and work your way up the settings until you can't understand the information being presented to you.
I can still get all the words at 1300WPM, I start losing about every third word at 1400, and anything 1550 and over is a comprehensive mess that I can't get anything out of. My roommate did this for me so I could get a sense of whether it was good or not, and he ended up not being able to go over 400.