Full disclosure: I am highly biased and naturally inclined towards the type of French food that La Banane serves. I'm also a sucker for the Art Deco/1920s-style interior which, like the food, is a bit of a throwback but also has some modern touches. The food complements the decor and vice versa.
If you like to eat things which are heavily sauced, pastry-encrusted, served with caviar and definitely off the Weightwatchers chart, come here. Prices are on the high end for Toronto, and the area, but the portions are surprisingly massive. (Our $27 crab claw plate came with, I think, four whole legs and claws, for example. And the trout, a dish for one, was at least an inch thick and must have weighed close to a pound.) I'd say order less than you think you need, but that would ruin the fun. Eating at La Banane feels like a celebratory occasion, even if you have nothing to celebrate.
Only nits for me are the fact that it was extremely warm in the restaurant (or at least in the back room) and they should give you a nice little finger bowl if you are ordering from the raw bar, or at least something as messy as the crab claws. It'd be a nice touch and one I think the decor and feel warrant. (I'm also generally hesitant to give 5 stars to a place that's only been open a couple weeks. I like to see consistency.)
Bottom line is they've done a world-class job of creating a certain atmosphere here, from the food to the design to the music. If you want to show your friends from out of town -- friends from much cooler places than Toronto -- that Toronto can be cool, take them here. Or just come if you want to have a good time and eat some good, diet-ruining food.