I'm the same way, I don't like using the touch pad on my laptop either. I was a little skeptical of the touch screen for typing. I am coming from a Palm Treo and text messaging/typing was very easy, on my iPHONE, it's just as easy, if not easier. It took me a couple days to get used to it but it is great, no complaints here.
The touch screen on the iPhone isn't like the trackpad on your laptop. You don't have to constantly keep your finger on it to navigate. Taps and swipes are all you need. It's not a constant input, because you're not moving a cursor... your finger is the cursor.
But... go try it again at an Apple Store. Play with it some more. It's not like you're gonna be using it as a laptop replacement. (However, If you're thinking of using it as a mini-laptop (to replace carrying around your real laptop) then it probably isn't the phone for you. You'll probably do better with a Windows Mobile 5 or 6 phone. Something like the AT&T 8525 or wait a month for the upcoming AT&T 8925.)