I really can't say enough good things about the Walks of Italy tours and guides. This is definitely the way to go.
So, we had the Pristine Sistine tour booked for this morning. With a 715 am meeting time, we definitely had to get up early. This one worked a little different, as when we arrived at the meeting place, there were enough people for multiple groups. I think there were 4 or 5 groups, each with their own guide. After being assigned to a guide, we walked to the entrance of the Vatican Museums. If you haven't been since about 2000, everything is completely different now. We walked to the entrance and then had to stand (with all of the other tour groups) for about 30 min. Once they open the doors, you have to wait for the guide to get the tickets (and kids under 18 have to show themselves at the ticket window). We also took a bathroom break. We also realized at this point that there was a young woman in the group who was having some sort of health issues. While I felt bad for her, this slowed us down a lot, and is a real drawback to a tour like this.
Anyway, we made it to the Sistine Chapel pretty fast and had 20 minutes to look around. It wasn't very crowded, and I was actually able to sit on a bench. I honestly didn't even know there were benches on my previous visit, it was so packed. Our guide was not allowed in (although, I don't understand why, as there were other guides in the chapel), but she gave us more than enough history and info (including a handout) beforehand for us to enjoy on our own.
After that, we wandered through the galleries for a few hours. By about 10 am, the crowds had become significantly worse, and I was starting to wane. The last hour was tough. We also made a loop that took us back through the Sistine Chapel a second time. I was kind of dreading that, based on the crowd levels, but it wasn't as bad as I expected.
Anyway, we saw all sorts of stuff - statue galleries, the Raphael rooms, the collection of modern art, a couple of courtyards, and really more than my brain can even process.
We didn't get to the Basilica until almost 11 am, and holy Moses, was it crowded! We did not get anywhere near the Pieta, and we were literally pushing through crowds. Our guide did an awesome job, considering the circumstances, but I could tell she was exhausted (as was I).
Originally when I booked, I was tempted to do the more comprehensive 6 hour tour. I'm so glad I did not! First of all, at the end of Pristine Sistine, I just wanted to be away from the crowds! Second, I'm not sure I like or appreciate art enough to spend more than 3-ish hours there. It's just a lot to absorb!
Overall, I'm glad I booked this tour and saw the Sistine Chapel the right way (last time it was elbow-to-elbow people, and I had a broken foot). The crowds are really an issue with the Vatican and their less-than-stellar management of crowds/attendance. I would love to have had a more comprehensive tour of the Basilica with less crowds, but I'm not disappointed. The only other drawback is the hurry-up-and-wait aspect of the tour, but our guide handled that at best as can be expected. She can't control what time the doors open. The Vatican is a crazy-busy place, and I'm glad we were able to do as much as we did.