Skip the line pass wasn't necessary for the time we went. It was nice to show up with tickets in hand, especially since this was the very first sight-seeing adventure we did once we got to Paris. We went on a Sunday morning and there wasn't really a line to get in, but I imagine that at times, there might be. If you are on a tight schedule, this is a relatively inexpensive skip the line pass and could save you some time. I'm a planner, so having everything beforehand gives me peace of mind.