We always get a car when at WDW, partly because we like to visit other resorts, and Disney's transportation isn't really geared to make that easy. But we also use the buses, and have no complaints about OKW's transportation system.
Here's one tip that has worked for us. All of the buses make their stops around the resort in order. If you get on a bus at its first stop, you will have the opportunity to tour the entire resort when you're all eager to get to the park. But on the way home, you'll be the first ones back to your room.
On the other hand, if you get on the bus at its last stop, the Hospitality House, your next stop will be the parks. On the way home, though, your exhausted family gets to take that same tour of the resort. It's not terrible (our kids are usually asleep anyway), but not ideal either.
So check your OKW map. Many times your room will be close to two stops, and one will be good for the trip home while the other is better for the trip out. Buildings in the 20s are perfect for this, being close to the first and last bus stop.