I've been riding 23mm tires @100+psi on the streets of Chicago for two years with one flat (pretty aggressive nail).

When I first went to the thinner tires (from 32mm) I had a lot of flats, mostly pinch flats and stem-related stuff. Learning how to properly seat the thin tires took care of the pinch flats. When I got a new bike (with, of course, new rims) I no longer had any trouble with stem flats either.