I agree with jaysue. I've always gotten to the park using the bus by park opening, and waiting at the bus stop or waiting by the turnstyle is one in the same to us. On occation, we've had longer waits, but never when we were in a hurry. We also do the flex thing - having watched the bus to Epcot at WL pull away while we were walking to the stop, we took the bus pulling in to the TTC and the monorail over. Takes a little longer than catching an immediate bus, but less time than waiting for the next bus. And, my last airport car rental experience took over two hours - that's a lot of waiting for buses. (I can assure everyone that any Disney bus stop is more pleasant waiting experience than the the garage Budget uses for pick up.)
The kids LOVE the buses, to them they are another attraction (along with the monorails and the boats). We don't take buses at home, so the kids think its a real treat to take buses all week.
But I travel differently than a lot of people. The inconvience of a Disney bus is a cakewalk compared to trains in Ireland or Italy, buses in Thailand, air travel in the former Soviet Union (oh, sorry, plane isn't leaving today, come back tomorrow, it might leave tomorrow, all communicated in some mix of my bad Russian and their bad English). I've never had to sleep at a Disney stop, or walk eight miles up the mountain to get to my destination once the Disney bus drops me off.