Keyzen itself actually has the benefit of training typing on all of the symbols on the keyboard, something that "Keyzen Words+Plateau" seems to throw away entirely, unless I'm missing something.
Some random ideas I have about it (since it's easier to talk about stuff than to build it): * Your quotes are all from famous books and movies, and you have affiliate links to Amazon... brilliant! * Do you have a mechanism that minimizes repetition? * Do you ever need to fake competition? * Could you visualize mistakes as crashes, to keep things exciting? * Consider making a keyboard UI for the site (Although I use vimium) * Build a mechanism to challenge your friends. * Analyze history and plot it. Take into account difficulty of paragraphs (come up with difficulty rating based on your user data). * Give typing tips; perhaps it's enough to analyze words that the user mistyped, and offer them more passages with them. * Improve the CSS. The UI should reflect the incredibly high level of polish in the gameplay.
Maybe I'll have more random ideas when I play it tomorrow. ;)