Super easy! People who didn't have tickets beforehand looked miserable sitting in the heat in an immovable line. But it only took me about 10 minutes to get inside, find the audio guide booth to exchange my voucher for a ticket, and then scan my ticket at the entrance. There's a very clearly marked booth to pick up your actual audio guide after scanning your ticket. The guide itself didn't have much information - only about one thing per room, but these seemed like plenty to me given the vastness of the museums. There was plenty of information about the Sistine Chapel too. I enjoyed going at my own pace rather than staying with a tour guide. Definitely crazy busy though - expect crowds and heat. But there's a water fountain to refill water fountains and plenty of restrooms!

Skip the line is the only way to go...Our tickets were for 3pm. I thought that this would give us plenty of time to get through the museums and get to Saint Peter's Basilica before it closed for the day at 5:50...we were not so lucky. I think if we had gone faster through the museums, we could have made it. My advice is to watch your timing so you don't miss out on the Pieta and the beautiful Basilica.

The process was smooth. I was allocated an entry time in the evening by the system automatically, and I called the customer service to ask about it. They suggested that I could try going earlier. It turned out that the ticket office at Vatican Museum wasn't strict about the time slot. And the exhibition was definitely impressive.