In fact, there is no equivalent in the American constitution to the French PM. Or imagine that, when the president appoints the Sec of State, of Defense, the Attorney General, etc, he also appoints a coordinator of executive activity. Sounds stupid because the president is in fact (with more or less help from the Veep) that coordinator.

My personal view is that the French system on this point is full of BS. The PM is there to support a polite fiction, which is that the president is above the fray and doesn't mind the shop. The PM's work is real, but his main function is to make it look as if things are getting done, and to take the rap if not. He is often a lightning conductor for the president -- he gets fired when things go wrong, the president sails on regardless.

That leads to an answer about whether it's a vote of confidence to be appointed PM. Yes. But it's a very risky position. Ideally, a presidential candidate would want to keep away from it. (So why did Villepin take it on? No doubt because he has a high opinion of his ability to make France fall in love with him [his actual words on this seem to have been more buccaneering...])