For a device like the Touch Diamond2, the on-screen keyboard is super important since it has no keyboard.
In the first generation Touch Diamond, HTC brought a keyboard that was far superior to that of the default built into Windows Mobile. It allowed for use with fingers and not just a stylus, and it came in three flavors: T9, SureType, and full QWERTY.
It looks like the Diamond2 (and presumably all new HTC devices like the Touch Pro2) will come with a refreshed keyboard, shown below in the comparison. The bottom image is taken from the Touch HD, and the top image (courtesy WMExperts) comes from the new Touch Diamond2. Note the inclusion of the D-Pad buttons. Also, the borders of each key is more pronounced. The biggest improvement is the elongation of the space bar, thanks to the replacement of the ABC/T9 switch to a higher location. This extra space allows for a dedicated period key, plus it shrinks the button that calls up the number row. Overall, it looks like a good refresh. Get used to this keyboard, we’re going to be seeing it a lot!