The Paris Museum Pass may be a reasonably good deal for many tourists, but know that it does not ensure your admission to the 60+ attractions advertised.
My wife and I bought the 4-day, €62 version of the Paris Museum Pass. We planned on visiting the Louvre, the Orsay, the Catacombs of Paris and the Arc De Triomphe. The cost of individual tickets for each was roughly equal to the PMP, but the 'skip the line' promise in tourist-crazed July seemed worth it.
And it would have been, had we not been denied entry to the Louvre with our Paris Museum Pass. We went late on Wednesday July 17/19 (about 5 PM, planning to use the evening opening hours) when the staff member at the "patrons with tickets" line told us that there were so many people inside that they could not allow anyone else entry. While we were quite disappointed (this was our only window of opportunity for the Louvre on our stay) we would have understood, except that patrons who had purchased their advance tickets directly from the Louvre website were still being admitted. So it wasn't actually "full"...if you'd given your money to the Louvre directly you were still welcome. The Paris Museum Pass not only did not allow us to skip the line, it meant we had wasted our money.
Their fine print online does day "Exceptional closures and free admission (strikes, public holidays...) will not give cause for any extension of the duration, nor any refund for one or several days." We're not sure this applied to our situation, since it was not a closure (again, those smart enough to pay the Louvre directly were still getting in).
I simply offer this cautionary note. I'm sure this capacity problem at the Louvre is uncommon, and that in many cases the Paris Museum Pass delivers as promised. However, if you want to GUARANTEE you'll see the Louvre, buy your tickets in advance directly from the Louvre site. Patrons who who've paid the museum will be given preference if a problem arises.