Just like any mass transit, we've had some hiccups, but overall have been extremely pleased with our BC experience. And after a stay at AKL with buses (first time at AKL we had a car), I swore I would never again complain about BC buses lol. And there was a lady firmly speaking with her husband saying "THIS is why I wanted to stay at BC again..I will NEVER stay here again!". Anyways..back on topic.
The only bus we didn't find efficient was the DTD one. However, no DTD buses are in my opinion, so we always plan to just take the bus there and then either take a taxi home, or our accidental favorite, take the boat to POR, walk around the beautiful grounds to their buses, take bus to Epcot, walk through Epcot (hitting an attraction or two) all the way "home". Our kids keep talking how this was the best day ever! Of course you need Park Hoppers for this one.
We take the boat to DHS, walk to Epcot (the sole reason we stay there), and bus to MK or again, walk through Epcot (World Showcase is closed until 11, so there is literally NO one walking back there..it's so peaceful, great photo opportunities!) and then hop on the monorail. AK obviously needs a bus, but we didn't find it bad either. I am very glad they no longer share with Swan and Dolphin and BWI, as that made the ride home from some parks almost torturous.