Linda is 100% correct. I hate that All-Stars gets a bad rap because they sometimes share buses. Lots of the resorts share buses. CR, Poly and GF share buses for every trip. BW, Dolphin, Swan share buses. YC/BC share buses. POR/POFQ sometimes share not to mention all the bus stops inside each resort. Yes All-Stars sometimes share buses but at least the resort are right in a row no more than a minute drive to the next resort. I'd rather do that than to stop at BB on the way to Epcot like AKL does.
With All-Stars, in the morning you will get your own bus to the parks, as the number of people slow down they will start traveling to the other All-Stars to pick up more people (think of it as being green, sure it might take 5 more minutes but think of the fuel they are conserving). At closing time at the parks you will get your own bus back. A good thing is if you are staying at Music you can jump on Sports or Movies if you don't want to wait and a have a few minutes walk to your resort.