I toured in November, 2007. I purchased a guided tour through Presto Tours of the Vatican. Was a little pricey at 55 euros but in the end it was some of my best spent dollars on my entire Italy vacation. You can also purchase through Presto (and others) an entry ticket which gets you through the door but does not have the guided tour with it for 20 euros. I found the added guided tour excellent.
Our Presto tour guide (Mya) had studied art, history and archaelogy so was very well informed and very well spoken (english tour). I'd highly recommend her. There are other cheaper tour companies and they may also be good as well but can't comment on their quality. Our tour was a solid 3 hours of speaking by the guide and we had a small group of 10 that day so made it very managable. She gave us a lot of the hidden secrets of the Vatican and also gave us the church's version and the history that science and archaelogy have found to be true. I really enjoyed hearing both versions but those more religious than I may not.
Mya was there on time and where we were directed to be. She made sure we got our money's worth and kept the discussion lively. The only negative was that our guide did not have a mic so that did make it hard to hear her in the noisier parts of the Vatican. If they improve on that, there wasn't a negative I could name. Excellent tour.





