I love French Food and having lived in France for numerous years makes me very particular.
I enjoyed Mon Ami Gabi very much. The food is not the "over the top" French fare of many LV restos but rather a more comfortable bistro fare (think steak frites, mussels, roasted chicken, etc).
My pate was quite good and came with pearl onions, cornichons, and grilled baguette toast. The toast wasn't quite grilled enough for my liking, and they took care of this issue very quickly. Otherwise the rest of our food was excellent as was the chocolate cake dessert.
I would recommend reservations if you want to eat... we lucked out and got a table with a view of the Bellagio fountains. Otherwise come prepared to wait in line for a patio seat.
The bar area is very cozy, and the bartender made us a few stiff drinks while we waited on our table. The wine list is very small but very high in quality. The prices are very reasonable.