I've been using clipless pedals for over a decade and couldn't stand to ride more than a half a mile without them. Trying to ride just with my thigh muscles and changing back to that "mash/mash" pedal stroke would drive me nuts. Also I think my foot would come off on every stroke.
I used to use SPD pedals for the road after starting with them on my MBT thinking that keeping the same system would be a good idea, it wasn't. I really didn't like the experiance as the cleat and pedals are tiny (my MBT pedals have a platform around the SPD mechanism) and eventually switched to a more road spacific pedal for my road bike, I suggest SPD-SL as they are easy in and easy out while providing you with a stellar connection.