There's no control over the insertion of spaces, it automatically inserts one after you release your thumb at the end of a word. So if you accidentally delete a space that you need, which is likely during the learning process, there is no way to get it back without also deleting the character before it and adding an auto space. Also there is no way of preventing this automatic space either, so web addresses and the like have to be entered as one very long continuous gesture, without any mistakes; if you make a mistake you must release your thumb to hit the backspace button, which you must now hit twice because an unwanted space was just added.

Finally, the learning process is heavily hindered by the fact that your thumb obscures at least one or two of the 'branches' during a gesture, which means when you have to visually consult the screen because you have forgotten the unusual spatial model (the direction matters too remember,) your only option is to pivot your thumb without it leaving the screen, and hold your phone at an odd angle so your can peer beneath your digit and decide where it should go next. Not very practical.

Give me a spacebar and the ability to disable autospacing and I'll try it again. Until then I'm sticking with swype, which allows me to type extremely fast.