If memory serves, which it doesn't always, the WL shares with FW when heading to EPCOT, when headed to the AK or HS, the WL shares with the GF.Buses at AKL are actually quite good. They only share with The Villas at AKL next door. I think WL will share with other resorts, but I am not positive of which ones.
The only real issue with AK and the buses is the resort is physically farther away from the other parks save for AK. This adds about 10 minute or so of travel time.
I've never taken the bus from the WL to the MK.