See:
googlecreativelab#9
Set of letters {A, E, H, I, M, N, O, S, U} repeat at near about 5-6 times the frequency of other letters such as {B, C, F, G, P, Q, V, W, Y, Z,}. Infact the moment letter Z was first shown, and I entered the code, the learning sequence ended for having reached the count of 26 letters and switched over to the numbers.
I'm not sure if this is true (I havent personally got this far) - but if it is we need to fix this