Overall, I was very impressed with the TypeFast software and will probably be using it for all of my Windows systems. It's very clean and well laid out -- not to mention that it's among the smaller number of typing tutor programs that allow for the possibility of other layouts (which is really nice because lessons for QWERTY are not appropriate for learning Dvorak.) One reason I will not be using it in linux is that I have found the ktouch program to be better for me (you can find it here, so you might want to check it out sometime.)
One of the biggest reasons that this is so is because it can be kind of disorienting and hard to follow every time you hit the end of the line it sort of jerks over, like some kind of autmatically wrapping typewriter or something. Ktouch, on the other hand, smoothly (with optional speed adjustments) scrolls the text to the left as you go and it also tries to keep things down to one line without breaking any "words." It's also nice how at the end of each line it has you hit enter to move to the next, which gets that enter key into the lessons as much as it needs to be (I saw a thread on this elsewhere here and think it works great as a solution.) This method feels more natural and less disorienting. However, even if you do not implement a system like that, it would at least be a little more natural if you try to keep from breaking up "words" so that it isn't jerking over at the most confusing times.
P.S. You might want to take a look at the way it automatically increases/decreases lessons based on (adjustable) speed/accuracy performance goals without requiring the full completion of the lesson. While their default settings are too lenient IMO, the system serves very nicely to relieve the user from the tedium by mixing things up a bit rather than doing only whole lessons at once. It made it more interesting for me to keep going for me at least. Other than this and the text handling, I actually liked the look and feel of TypeFast a little better besides the fact that it's just nice to have something a little more universal since ktouch was intended only for KDE environments really (though it is simple enough to work in even Ubuntu which I think only keeps a fairly minimal number of KDE packages around.)
P.P.S. BTW, when I tried it, TypeFast worked flawlessly via WINE in linux except that the game dids't work (unfortunately, I'm having troubles with 3D acceleration on that system, so it really doesn't say anything one way or the other that the game did not work for me.) Perhaps a port using libwine might be a better choice than native QT since linux appears to not be a big priority to you. That would allow you to focus more on finding Windows code that works flawlessly in both environments (which I suspect mainly just means a little tweaking in the 3D environment -- if even that.)
