We always go for two weeks anywhere between early August and late September and in all my trips and visits to DHS, I have never waited for the GMR. You walk in and straight on at any time of day. I've never even had the chance to watch the preshow in the theatre. I check the MDE wait times every now and then throughout the year for fun and is always 5 or 10 minutes. It's not the super popular always 60 minutes+ wait people are now making it out to be. I'm know people are upset but whining about how awful 'Mickey' is going to be is not going to change Disney's mind.
First, you need to play the lottery if you never had to wait to ride this attraction, even recently. With luck like that you'll do well. Second, no one here is saying that the lines are always 60+ minutes. We are saying that the queue is sometimes filling up at least half the switchbacks. Even that would only amount to a 20 minute (at best) wait. Third, no one is whining.