It is exactly one of overrated place in Rome. There are much better places in Rome to visit without any line to wait for hours. Go to Pantheon, Piezza Popolo, etc...
On a visit to the vatican museums, When leaving the sistene chapel do so through the exit at the very back on the right corner for groups. Brings you out at the doors of st peters avoiding queues.
Don't buy anything in the shops around the Vatican City. Everything is super overpriced (e.g. 48€ for a 2gb memory card, 8€ for a piece of pizza, etc.)