I was able to read the article I chose in about 85% of the time of the default 400WPM of the bookmarklet (I read the article first with a timer, and then reread with the bookmarklet), which would put me at 470WPM. With Squirt, I was only able to get up to 650WPM before it felt too uncomfortable.
I wonder if people really read one word at a time, especially when they're short words. If people do read more than one word at a time, I think a more intelligent approach might be necessary to really make the experience both comfortable and fast.