Income taxes for US ex-pats

OK, I've asked this before and I'm going to try again. Before moving to another country, I think it is important to know how their taxation system affects US citizens contemplating a move abroad. Is their anyone in France that can explain to me in a clear way how their system works. I know that they have a tax treaty with the US so we are not taxed twice. However, I'm led to believe that there could be additional income tax imposed by the French on US income. For example, any tax that the US gov't has set at a 0% rate(lower brackets of qualified dividends, capital gains and municipal income). Would that be taxed in France and if so, at what rates? Come on you US ex-pats, some one must have an answer somewhere! Thanks for all help.

FATCA is a royal pain in the ...
What you should do is go to your nearest friendly tax attorney in the US, who will explain everything for you.  Ask him for the specific details you have in mind, and tell him to leave out everything else.  Then go have a drink.

It all depends on if you are considered to be a "resident fiscal" in France. 
You will be taxed on income in France if you work in France.
You'll have to provide yearly tax reports for US income if you hold a carte de sejour, but won't be taxed on that income.
When I sold my apartment in Paris, I had to pay capital gains taxes in both countries, at two different rates.

Thank you for your reply. So what you are saying is that all income declared and possibly taxed on your 1040(even taxed at 0% rate) will not be taxed by the French gov't? I don't like the concept of filling out a form and mailing off to the French authorities each year and waiting for them to get back to you on how much they think you owe them without giving you an explanation.

With FATCA, US citizens do not have a choice.  You must file a form each year with both countries.  You can set up your account online, if needed, and see how much you owe immediately. 
If you're living in France now, go and see a notaire, who will let you know if you are considered a resident fiscal or not.  That's the important thing.  You should also consult an American tax attorney.  There are a lot of grey areas when it comes to income and where it's earned, now.
Failure to file a yearly report - even if you owe nothing - can result in significant fines.