Hi,
I too am asking this same question.
I currently have a Sony Ericsson Xperia Ray and it has the wonderful feature of being able to seamlessly move between phone keypad input and Qwerty by simple rotation of the handset - the best of both worlds.
Oddly enough after 8 months using this phone I find that most of the time I want to use the keypad T9 predictive input. It is faster and I can use it single handed and type with my left thumb. Also I don't need to get my glasses out to see the keyboard as it is much larger. I can actually type a text without even looking, if necessary. I've also done a speed and accuracy test and find that the keypad wins every time for me.
But for work purposes I'm going to have to move to an iphone eventually. But this lack of T9 (and the rediculous monthy cost £36 compared to £20) is making me stick with the Xperia Ray up to now.
This MultiTap text is presumably also T9 predictive? But you say it wont integrate easily with the iphone?? Do you mean if you need to reply to a text you have to call up the app...it doesn't just appear as an option?
Many Thanks