Agree with above post about the times. Typically, if there is a boat in the dock, or on the way from Epcot/ Boardwalk, we take the boat. If we just missed the boat or don't see 1 coming, we walk. And we usually beat the next boat to the Studios.
Lobby to ticket gate is 1.1 mile, which is 22 minutes for the average walker (3mph). 15 minutes would be a fast walk (4-5mph). A walk with children or slow walkers will be closer to 30 minutes (2mph).
It is faster to walk and the walk is level, no hills, but it took me 15-20 mins and I would not want to do it in summer heat. Luckily I made the trek in December. Also would not want to try to drag a child on it unless contained in a stroller.