We did, in May. You get on near the International Gateway, right outside it... you stop at each of the Epcot resorts (Swan/Dolphin, Y&B Club, Boardwalk) and then you travel onto MGM.
As the previous posted said.....We went to MGM late one morning and the crowds to get in were outrageous! We hopped on the ferry (just outside the entrance of MGM) and took a nice relaxing ride to Boardwalk where we ate breakfast. Then we hopped back on the ferry which stopped at the YC/BC and then to the "back door" of Epcot. It was just now 11 in the morning and the worlds had just opened! Perfect!
So, if you don't mind a couple of stops on the ferry, its a nice ride!
The Friendship boats run between the International Gateway of Epcot (back entrance) to the Disney Studios. They stop along the way at the Boardwalk, Beach/Yacht Clubs and the Swan/Dolphin.
Nice leisurely ride, maybe 30-40 minutes total time. Much faster to walk, but it's a nice break to ride the boat.
There is a ferry boat (it is huge!) that runs between MK and TTC... That is how we usually get to the Poly for dinner at 'Ohana, we boat to TTC and then walk through the Poly.. Nice stroll.