The three built-in text entry methods are Full QWERTY, Compact QWERTY and Phonepad.
Full QWERTY is simply a full QWERTY keyboard as we are used to seeing them. Â Despite the large 3.8 inch screen on the Touch HD the keys are still pretty small for my fingers, and with or without T9 hitting the right key still takes concentration, and any attempt at speed will likely result in errors.
Compact QWERTY works like SureType, having 2 letters per key while still preserving the traditional QWERTY lay-out. Â Without T9 typing requires some concentration or a lot of practice to remember which keys require 2 presses. With T9 however that concern completely disappears, and typing is fast and even effortless. This is my recommended text entry system, as its fast, easy to use, does not require practice and pretty precise.
Phonepad is HTC’s homage to the 12 key cellphone keyboard and its many adherents, who may be very practiced with this keyboard. Â Without T9 it is again quite a trial, and even with T9, due to lacking the QWERTY structure, you do sometimes have to concentrate to find the keys. Â People who are however practiced in this keyboard (coming from a Nokia smartphone for example) may find this keyboard the fastest one to use.
In summary, while keyboard preference is a personal choice, I would recommend no-one struggle with Full QWERTY and rather use Compact QWERTY for less frustration and increased speed, and always with T9 enabled.