We were there! It was our first trip so I'll try to be accurate - compared to THursday and Friday, Saturday was busy but still not bad at all. We were only in MK for about 1 1/2 hours to quickly do some rides missed on Thursday/repeat some rides. We did the teacup, pooh ride, philharmagic, stitch and I think that's it. Stitch AND pooh were malfunctioning first thing in the morning so we got a fastpass for stitch and came back to pooh - still, we never had any bad lines at all and never waited more than 15 minutes for ANY ride. Fastpass was hardly any wait at all. Thursday and friday we walked onto almost everything (MK and MGM)
Have fun!