In the past, we have always heard buying the Museum Pass and using it at Versailles allowed you to skip the long queues. We had a terrible experience with the lines this week that seems to be getting very common.
Basically, the line to get in with a museum pass is still 2-4 hours. Even if you have the museum pass, you still have to wait those hours in a long serpentine line in the courtyard.
We actually left after being told it was at least a three hour wait to get inside. We talked to people who got there at 9 and they had a 2 hour wait.
The crowds were terrible. When we returned we checked TripAdvisor and there are so many complaints the last 6 months about horrible crowds inside and long queues. Even if you get a passport time online you can face claustrophobic conditions inside.
So, be warned things have changed. A Museum Pass did not allow you to skip a long line. As I said, TripAdvisor had many reviews and pictures of this situation.
Just a heads up!