I didn't read through the links, so this may be repetitive.

The museum pass certainly does allow you to bypass lines, and sometimes the time savings can be huge. We were there over Christmas, and one day the line at the Louvre was enormous. We walked right past many hundreds of people (who were not moving much) and walked right in! My guess is that the wait for the folks in line was at least an hour -- and that was at the mall entrance.

I also liked the option to come and go as we pleased. The Louvre especially can be pretty daunting, so we went three separate times in a six-day period. Each time we only stayed for an hour or two, and we explored totally different areas.

We'd use the muesum passes again in a heartbeat.