That’s really neat. You might explain why people would want to pay $29.95 because it is not exactly clear why we would need to pay. The practice feature is mind blowing, and works really well. Congrats.
Currently all of the lesson content is locked down (if you've created an account using the HN signup code, then you get to see it all, such as it is).
I've gotten lots of feedback to the effect that $29 is too high for a webapp, so I certainly will revise that down before launching.
Thanks for the feedback!
As for free vs paying feature, I’d only give the time taken to complete the exercise and the wpm, and suggest upgrading to the paying version to have more stats.
By "more stats", do you mean the accuracy statistic that is computed for each practice? Or do you mean the wpm/accuracy chart that you see on the Progress link?