Before I had my iPhone, I was all about T9. For someone who's borderline obsessive compulsive about typing full sentences, full words, and with proper punctuation at all times, it really helped to use the T9. I became so adept with it that I was able to memorize what order which words appeared in and type out full texts without so much as a glance at the phone.
LITTLE KNOWN FACT: WHEN YOUR PHONE GUESSES THE WRONG WORD, PRESS YOUR DOWN BUTTON. IT WILL GUESS THE NEXT MOST LIKELY WORD. In this way, you can type out the first couple letters, then just press down until you hit the right word. If you just keep adding letters, it will keep guessing but not actually insert your word until you hit space or period or whatever else.
Anyway, iPhone did away with all that. The full keyboard plus reasonably accurate word guessing software took some getting used to, but now I've no problem texting out full messages in a matter of seconds.