I have done this a couple of times. The first time I was asked if I wanted to and the second time, I asked if it were possible. Both times I got a co-pilot license without having to ask for one. It's really cool to see what's coming ahead of you and also makes for a great picture opportunity.
We did it on our Honeymoon...My husband was nervous to ask and afraid to look silly, but he went along..Now we do it whenever we're down there. The kids "expect" it!