It's quite interesting how damn near impossible it is to balance a game like that. When I first released it, it had no expert mode. I tried to make the normal mode challenging for most people without making it too frustrating. The feedback I got was mostly "it's way too easy", but I also got a few comments, particularly on Kongregate and other sites that appeal to younger users that "it's way too hard".
I also got a few emails from school teachers wanting to use the game with their students. Even the normal mode can be extremely frustrating. To please everyone I would need at least 3 or 4 different settings, I guess.
tl;dr: The touch typing speed among the population is fantastically diverse.