The location and transportation to the MK from the WL is fantastic. It is both speedy and relaxing at the same time. It runs very, very regualrly. Meaning you don't have those gaps of 45 minutes waiting on boats.
I stayed there twice this summer. One morning I decided to try the buses to MK because the boats don't start running unitl 30 minutes prior to opening, the buses speed advantage, and I wanted to be there before rope drop. So i waited on the buses. For some reason, it was unusually slow getting there and it ended up taking much longer and I missed the opening ceremony. Take my advice, when in doubt, take the boat. I didn't take a bus again to MK after that though.
One thing though, on my arrival night, I wanted to get to MK in time for Spectro and a hot dog at Casey's. Spectro was at 10. Long story short, the boats can be held back while the Elec. Water Parade goes through the water bridge between the lagoon and bay lake at about 9:20 or so. You do get to see a beautiful display, but it also impedes your progress if you are cutting it close, so be aware.
Regarding the other parks, this has been my experience. Going to Epcot or DHS, the bus stops at FW Outpost before continuing to the parks. To me, it seems as if this takes forever. I would say that 20 minutes is a best case scenario. Regarding AK, I have been told that the bus first goes to a monorail resort (GF), before continuing to BB, then finally going to AK; therefore, I have never used the buses to go to AK. I drive.