Wife and I are spending 2 M in France, starting w 4 days in Paris. Observations:
1) If you have a pocketknife, do not take it to a museum or church. I lost one at St Chappelle
2) Rick is obsessed with "online ticketing" to save the time in the line. This is not always good. We wanted to go to Musee d'Orsay. Online it said "Ticket + audioguide - E47" They don't give online the ticket alone. We ruled d'Orsay out. But when we went to Musee Rodin, we found a combo tix for E25 for Rodin-d'Orsay.
3) Lines are short in January. Musee d'Orsay was crowded. I cannot imagine June.
4) If you have mobility issues Paris is not a good choice. The metro is not accessible for wheelchairs. Sidewalks are narrow everywhere.
5) For a good inexpensive French traditional restaurant, consider the Boillon Charpatier chain. The food is good portions are not huge. The house pledge is to deliver a full meal (sans alcool) for E20. We ate there and it was good. 20 minute wait in line with dozens of persons, a lot of young persons. Several of these around Paris.