When the split keyboard was announced in iOS 5, I couldn't be happier. Using it though, the keyboard felt uncomfortable. Took me a few minutes to figure out why...
The problem is the order of the keys was contradicting my spatial memory. Look at the animation below and pay attention to the B.
See how it’s position moves from bottom left to bottom right of the H button? The relative position of row 1 and 3 to row 2 changes. The QWERTY doesn't have this issue as you can see below.
What to do?
One option is to stretch the backspace and shift buttons to position the rows back to their original position. In the merged keyboard the keys are only slight offset, but I made them large enough to keep the vertical rythm that is present on the other side.
The setback is that the B and Y button are harder to reach and it disrupts the symmetry but I would still prefer it over the current version.