The best so far was the Polynesian. Right out the front door and short waits. This bus tends to park closer to the park gates than most of the others.
The years we stayed at the Contemporary we really didn't use the bus that much since the Magic Kingdom and Epcot were the two main parks at the time.
I'm surprised at all the CBR "worst" listings. We stayed at the CBR quite a few years and never had a problem. Of course, we're seldom in a hurry so the frequent stops don't bother us much.
I'm also surprised at all the All-Stars raves. We sayed at the AS-Movies a few years back and the bus service was terrible. We waited as much as 45 minutes for a bus and they all parked about as far away from the park gates as you can get and still be on WDW property (okay, an exageration...). Maybe we just hit it wrong, but the bus service was our biggest reason for never going back to an All Star.
Over the years, I've noticed that the bus stops at the parks tend to run from the deluxe reosrts (closest) to the value resorts (furthest), which is probably okay since we might expect a few perks for what the deluxe resorts cost, even the "cheap" rooms.
One thing I'd like to see is inter-resort bus routes to make is easier for dining at the other resorts.