Last year, I was at SSR and was able to use the online check-in. I opted NOT to, because we had three people on three separate credit cards.
There were three people in line for online check-in. We were the first and only person in the regular check-in. We were checked in as the third person was finishing up. That was a total time of ten minutes.
It would only be useful if you were checking in at a very busy time of day/time of year.