Our experience on the French toll routes is that you cannot use your swipe credit card. Cash is the only way to go and, there is always a cash lane. We learned quickly to have lots of 1Euro and 2Euro coins. The machines do take the Euro bills and do make change. A couple of times, the toll has approached 20Euro. The French have some of the highest toll costs per km in the EU. At the toll booths, there is usually a staffed booth on the far right. Here's a snapshot of the sign overhead the lane that you look for. It's the little blue man in the sign that you are looking for. http://gyazo.com/b30447a81e7fae7c61c6946280a4c7d8
We also found out quickly that there are two types of toll booths. On the highways, you usually stop at a booth and pick up a card. At an exit or at the end of the section of highway being tolled (if that's a word), you put the card into the machine and it tells you the toll needed. Occasionally, we would exit and find an exit toll booth that just wants a certain amount of money. We were confused when we first encountered these types of exit kiosks because we never picked up a card anywhere. For this type of booth, everybody pays the same. They just want a few Euro. No card needed. Pay the cash and the gate will lift.
As for fuel on the toll highways, the automated pumps out at the fuel islands will only take the chip and pin card. However, we usually were able to find an attendant inside with a machine that would take our USA swipe card. We didn't have any problems with the fuel.
As Alex says above, the French autoways are very nice and clean. Not too busy either. Expensive - you bet. Many citizens as well as the large 18-wheel lorries (freight trucks) choose to use the older roads that run nearby the autoways to avoid the tolls. We did a lot of these roads as well. Very scenic but it does take longer and they can become quite crowded in places. Lots of trucks.