OP, we always drive to WDW, so we drive our car to and from the parks. Our value resort of choice is POP, and the bus system there is HORRIBLE (JMHO, based on our first stay several years ago). To elaborate a little, this is what happened to us: you wait 10-15 minutes for a bus, and as soon as it pulls up, here comes a person (or 2, or 3) on an ECV that you didn't notice because they were waiting far behind you, by the building in the shade, with their entire party; and, by the time they board, the bus is full, and you get to wait another 10-15 minutes at least for another one, at which time, the process repeats itself. NOTE: I am NOT bashing people who ride ECVs, I had to use one myself on DD's first trip to Disney. I'm simply explaining what happened to US on our first stay at POP, that made us decide to always drive our car-we don't have to wait for a bus, and we get to and from the parks much faster (at least, it seems that way).
Now, on our first trip to WDW in 1992, for our honeymoon, we stayed at CBR (which was a value resort at the time), and thought their bus service was WONDERFUL. We parked the car when we checked in, and didn't touch it again until the morning we checked out. There was a bus stop within sight of our room, and we never waited more than 5 minutes for a bus. I guess this is why we found POP's bus service lacking. Again, that is JMHO. YMMV.