I do this and I've had some luck with it. Of course I've always offered the poor bloke in the middle the chance to move to the aisle or window.

I have booked my family A-C-D-F and think we got away with it once. Last time two people got between us traveling together in the middle seats and we swapped, taking a child out of F and moving him to B so they could be together. Instead of being grateful the guy seemed kind of miffed that we had booked our seats that way, so maybe next time we won't offer to trade.