Well, personally I'm using 5800 touch screen phones. My previous phone was Sony Ericsson C902.
The trend has been changed. Everybody's using touch screen phone/bb/i-phone.
But using touch screen phones you don't need to use any strength to press the button anymore. Can save ur finger energy. Haha. That's one of the reason I dump my C902. But seriously, touch screen phone are more comfortable to users. Besides, touch screen phones can be more accessible for those poor eyesight. Because icons sometimes can be easier to see than text.
My C902 after one month using it, it has keyboard problem. Thus I need to repair it. It charged me for 80 bucks! So expensive! I believe keyboard has separate keys which can break or not functioning due to dirt, crumbs, water damage etc.
Conclusion, touch screen phones potential to have a longer product life.
Besides, I've 2 touch screen phones.
I agree that touch screen phones are the fastest pointing devices, from all the reasons, I dump my old phone!
