I wanted to add to this from my recent trip early February. We bought MaxPass for one day of our multi-day trip. It was very nice to have that day, but it was easy to see first hand how much the fastpass line slows down the standby line. Nearly every cast member just lets the fastpass people right on through, while standby just waits. While in line for RSR, I had a good 5 minutes where I was able to observe the merge point of fastpass, single rider and standby lines. I think only one group of standby people were allowed to pass during that time, while numerous fastpass and single riders did. The people at the front of the standby line were visibly frustrated and irritated with their lack of movement.
They really need to limit the number of fastpasses issued or increase the ratio of standby people to fastpass.