It may be true in some fields, but it's not my experience. A lot of workers in France work more than 35 hours. In particular, most qualified workers (in the software industry for instance) don't have a fixed schedule and overtime isn't paid. To compensate for the 4 hours (going from 39h to 35h) they have more vacation days. It amounts to about 10 days annually depending on the company. Besides, some people are pressured not to take those day off. Several friends of mine work long hours (> 10) and don't take more that 4-5 weeks vacation a year (which is good compared to the US or Asia, but far from the promised 35 hours a week).