I just got back from Rome. Here's my two cents. We had Vatican Museum reservations for 1 pm. We went early, because this was all new to us and we didn't know how much time to allow for transportation and walking. I think as long as you arrive a little early or later (even by 1 hour) you will be fine. We found out the hard way that later is much better. If you can go at 2 pm, it will probably be much better. Allow about 2 hours for Museum. We got caught in a crush of tourists. So, we were unable to leisurely look at exhibits. It was more like crowd herding through. Honestly, it was far more crowded than I anticipated. Bring a bottle of water with you. Other important tips, a bus ride from Pantheon neighborhood to the square is about 15 minutes ride. Then, veer off to the right of the square and follow/walk along the wall to back area. This is the museum entrance. (Another 10 - 15 minutes). Ignore the left line (along wall) at museum entrance. Get in right side line and easily walk up to the entrance. This is the reservation line. Then, feel bad for those standing in line. Once you get inside, you go to a ticket booth upstairs and show your ticket voucher and photo ID. Allow 1 - 2 hours for St. Peter's Church. We were excited and actually budgeted too much time. We went at a slow pace, except for being herded through the museum.