I stayed at CBR in May 2015. I was there for the (now defunct) 24 hour day. We got to the bus stop at 5:40 AM (we were running a little late and understood we would probably miss rope drop). There were a lot of people at the bus stop, more than I would have thought. Then I heard a guy on his cell phone telling someone they'd been at the bus stop since 5 AM and hadn't seen a bus. As soon as I heard that, we turned right around and got in our rental car. On our way out, we had to pass one other bus stop and it, too, had a large group of people waiting.
We took a break later in the day, and when we went to return to the park, we waited a few minutes at the bus stop. A bus pulled up (there were a lot of people on it) and let a few people off but wouldn't let anyone on. I figured I had no way of knowing when a bus would come that we would be able to board so, again, we drove.
I didn't attempt the buses after that. Too much frustration. I feel bad for the people who missed rope drop after being at the bus stop an hour ahead of time.