Not very useful… It doesn't teach you how to use the keyboard, it just tests you. If you don't know how to do punctuation, for example, this won't really help. Also, it's set up for only the alphabetical layout, so it's not much use if you want to learn one of the other layouts. There's also no variety, just copying letters against a time limit. Check out 'MessagEase Game' to see how to do a good keyboard training app.
Needs instructions in plain English I'm giving this one another try at first it is a little strange but it does get easier and looking at the cheat sheet helps as well as using learning mode there is some word predictions The advantage is the small space it takes up both on the screen and on your device.