I can't imagine it'll make any difference at the hiring stage (I certainly interviewed my fair share of older interns and often found them to be very strong).

The only way in which I think it will make a difference is if you end up working for a large tech company which has an intern community. It'll be harder to fit in socially, but you won't be the only older intern in general -- some of the PhD interns I worked with were late-twenties, early-thirties -- so you won't be totally alone.