I definitely think the buses from/to DTD need more frequency. We spent a miserable night waiting over 45 minutes for a bus. And, as you can imagine, the line that formed over the span of 45 minutes was enormous. Thus, when the bus finally did arrive, it hardly made a dent in the line. I would have believed this was perhaps an isolated incident, except I've heard other tales of problems with DTD buses similar to mine.
Other than DTD, I never had a problem with the buses. Granted, there are lines and waits at park closing for buses, but I don't think there is much to be done about that . . .