I think all the "optimization" was a mistake. Instead of optimizing for the most-used keys, I think it's better to optimize to make it easy to remember.
Phone typing was easy to learn because the letters were both predictable (alphabetical) and because you could look at the letters when you forgot, especially while learning.
Since looking at the keys isn't possible here, I think it's even more important that being able to predict the locations of letters is possible and easy.
Phone typing was easy to learn because the letters were both predictable (alphabetical) and because you could look at the letters when you forgot, especially while learning.
Since looking at the keys isn't possible here, I think it's even more important that being able to predict the locations of letters is possible and easy.