Even though we always have gone to USF/IOA as a family we often split up and use the single rider lines. At USF there are single rider lines at the Mummy and MIB. The SRL at MIB works like a charm. They really have it down to a science there. At Mummy, not so much. Depending on who is loading the guests into the cars, it can move well or it can be a disaster. We've seen it go both ways. There have been several times I've seen cars go out with empty seats on the ends and people waiting in the SRL. IMO, if the single rider line doesn't at least get you near the foot of the stairs, skip it and just get in the standby line. It'll move quicker.
At IOA, Spiderman has a single rider line that usually moves quite well. I could be incorrect but I think Dr. Doom has a SRL also. (I've actually never gone on Dr. Doom. I made it all the way into a seat once, looked up and ran!!!) I have been at IOA a few times during very heavy crowd times when a single rider line was opened at Hulk but that is not always the case.
I think I got them all. If not, I'm sure someone else will let you know.
All in all, the single rider line is a GREAT thing!
