(This does not mean that touch interfaces are better, though -- just that they are more intuitive.)
My grandmother also figured out the iPad's UI quickly, although she has almost zero experience using computers, and struggles to work her phone. I didn't explore how much more she could do with it though.
Surprisingly though, my father in law, a doctor with some computer experience, struggled a little with his iPad, and only uses it for online banking. I think it had to do with un-learning his old habits.
What I guess from this very small sample is that a touch interface is more intuitive for novices, but could be troublesome for those with some, limited computer experience.
I'm sure there's tons of research being done into this stuff...hopefully it will be distilled into an accessible form soon [an updated Design of Everyday things say].
My 2-yr old has gleefully wiped my PIN-locked iPhone several times, as it was synced to corporate Exchange (Here Daddy! sigh Thank you, dear).