We booked a four hour tour which consisted of a visit to the Vatican museum, the Sistine Chapel and St Peter's Basilica. We booked this with http://www.rome-museum.com/tickets.htm and I would definitely recommend it as the tour guide really knew his stuff and made the tour very interesting.
As we were part of a tour group we were able to miss the queues which was brilliant.
The Museum, Chapel and Basilica receive on average 20,000 visitors a day so as you can imagine there wasnt really much space anywhere.
The museum was the longest part of the tour and there were so many facts about Rome etc that you would never know unless you had a tour guide.
The Sistine Chapel was a bit of a let down as it was filled to the rafters with people. You were asked to stay silent and not to take photos when in the Chapel however both these requests were ignored which made the experience less enjoyable. However the sight of the paintings on the wall and ceiling were absolutely breath taking.
St Peter's Basilica was definitely my favourite part of the tour. It was so spacious and it is the largest chruch in the world. We were informed that it is so big that you could fit the Statue of Liberty into it.
This review is the subjective opinion of a TripAdvisor member and not of TripAdvisor LLC.