We were there the first week of August...it had been 5 or 6 years since we stayed at BW and I could not believe how rotten the bus service was....yuck...only 3 bus routes come by there....1 to MK, 1 to Typhoon Lagoon and DTD and 1 to Blizzard Beach and AK. (boat service to MGM and EPCOT seemed fine.
We did not go to MK...but every bus we saw (all 3 routes) all week was packed....we never got a seat on any bus we boarded. BW is the 5th stop on all 3 routes (Swan Dolphin, YC, BC then BW)....often it seems the busses were full before they even got to BW and would go straight to the parks, by passing the stop....which means people were waiting a REALLY long time for some buses (especially to the parks in the AM), other times a bus would come by already packed and they would let 5 or 6 people on, leaving 20+ people still waiting.
On the way back to the resort we usually got a seat, but you had to make 4 other stops before getting to BW...my advice would be drive to the parks if you have a car.
We chatted for 30 minutes or so 1 afternoon with a couple waiting with us for the bus to DTD....they stay at the BW often and said that that week had been worse than usual for some reason. But they agreed that the bus service was worse for BW than most of the other resorts.