We were with kids, so wasn't really a chowhound trip. We rented an apartment on the Avenue des Gobelins, just below the Rue Mouffetard, which is a great area full of restaurants, mostly ethnic, and not a lot of tourists. One recommendation is Au Vietnam, which has great food with reasonable prices and nice service.
We had a pleasant meal at Les Papilles, but to me it wasn't worth the high praise it gets on all the blogs. The main course was soupy beans with carrots and a generous portion of fatty pork breast along with it. It was tasty enough, but let's face it, it was pork and beans. I like pork and beans as much as the next guy, but I was somehow expecting something a little more ambitious, based on more than just the flavor of animal fat. I also found the wine selection limited and uninteresting. The fact that it was nothing but tourists probably has some bearing. I think one can do better in Paris.
Great middle eastern pastry at the atmospheric La Mosquee, but dinner was strictly mediocre, so stick to the afternoon tea.
And now, for the most important caveat. DO NOT go to Tan Dinh. I found this place in an out-of-date guidebook which described it as upscale, sophisticated Vietnamese. It was not. The food was out and out bad. Some of the dishes were no more than simple stir fries, and for this we paid 180 euros for four people. And to think we paid half this price for the infinitely better Au Vietnam. When we entered, the very ancient proprietor, dressed in an elegant suit, personally greeted us, which was nice, but then he proceeded to talk my ear off the entire evening, and this in spite of the fact that I barely speak French. It was thoroughly obnoxious, and it was all I could do not to tell him to piss off. To add insult to considerable injury, they don't take credit cards, so I had to pay all my cash, and barely had enough to pay for the taxi back.
I should have had my doubts when I was able to get a reservation for the same saturday night. Apart from us, there was a big table of Americans, and two wealthy, eccentric-looking French couples who were there for the expensive wine list and personalized brown-nosing from the proprietor (I know everything about them, because the old fool gave me a running commentary). Anyway, run, do not walk, from this obnoxious clip joint.