We used it in June and it was fine. The line was long at the airport, but they are organized and it moves quickly. The issue is more with the people in line who aren't ready, didn't know what to do, etc.
Our luggage didn't get there within the 3 hour window. I spoke with bell services, and they said that it has been so popular that it is taking longer than they expected. Just prepare for that.
Pack clothes in your carryon and head off to the pool or parks when you check in. It was so nice not worrying about luggage, we just checked in with ME at the airport, boarded the bus, and arrived at SSR. Our luggage showed up sometime in the evening while we were enjoying Magical Kingdom. It was in our room when we got back.
FYI we also used gardengrocers.com and it was wonderful.