Barb,
MyVaticanTours.com is one of the larger tour groups in Rome. They, like many other tour groups, "own" the right to sell "skip the line" tickets. They purchase these slots DAILY from the Vatican for 18E. Then they sell them online for about 29E. Usually you are scheduled to "meet" their representative at the Group Entrance of the Vatican Museum. There they give you your access pass and your "skip the line." Usually they have a fixed time and sell a limited number of tickets. Only 1,300 "skip the line" tickets are sold for each hourly time slot!
If you can get a later time, I would as it would be less crowded.
Kent, regarding your question on the Sistine Chapel - once you get through the entry doors all groups and other guests move at their own rate. There is no "segregated" area for a standard tour group. When you get to the chapel, you are among the hordes - group or not. The advantage of a group tour is as you leave the Sistine Chapel you CAN take the group exit and drops you behind security at St. Peter's basilica (the door on the far back RIGHT). I often take this exit, although not with a group, as it helps you avoid the OTHER line at the Basilica.
There are a few, private PM (after hours) tours available. One of my friends is a tour guide and told me about these. They are expensive and are small groups - I believe he said $250 per person for a 3-hour tour. That would perhaps be the only way to avoid some of the crowds.
Ciao,
Ron
