It was randomly delayed for me as well (granted I'm using Chromium v20...). That (and the otherwise mentioned skipping to the next word erratically... and the not explaining visually how errors are handled) made it nearly useless to me. I would not be inclined to prefer it over, say Type-racer, except as a curio in the show-HN area.
The number at the bottom isn't updating at all (stuck at 0). Edit: refreshing twice brought it back– odd. I have to say though, it's quite a bit of fun. I'm not slow and I can already feel the push, I'm really glad you showed this :)
