JohnK, my ex-boss has some good thoughts on The genius of the iPhone’s keyboard that I have to agree with. I have a blackberry for work and find it very fast to type with, but a pain to have a huge form factor just to get that, and I also hardly ever text anyone with a normal phone.
I'm not sure that the iPhone isn't for the theoretical 17 year old who texts hours every day... I have a feeling that your teenagers will learn to text by feel on the iPhone, tactile feedback or not, just as they learned to text 26+ characters on a 12 key phone handset, though.
Worth a read, thanks John!