I agree with the above comments that this movie is not for the faint of heart. Even having visited theaters like that myself, to see it on film is still something that'll raise your pulse.
I think what's more important here than the content or 'weakness' or 'unwatchability' of some of the characters, is the fact that we as an audience member have suddenly become voyeurs into an ordinary day in these people's lives. We see them pursuing friendships, searching for affirmation, seeking pleasure from an addiction, the joy of anonymity, etc.
I think one example we can use is when you're out in the woods and you lift an old log, or a rock and look underneath. You don't disturb, you don't change anything, you simply observe and put the rock back down. Whatever life is happening under the rock was there before your arrival, and will certainly keep moving after you put the rock back.
The characters that exist in this movie certainly exist in our daily lives; gay, bi, jocks, trannies, married men, whether you're in Paris, New York, Akron, St. Louis, Houston, wherever. I think it's an interesting glimpse into lives that we might not get to see otherwise. The subject matter may be a bit edgy, but we have semi-comparable films (not necessarily content-wise) here in the U.S that are simply glimpes into lives.
I enjoy French movies. I think the French are more willing to challenge themselves through their cinema. If you can stomach it, take a look at any of Gaspar Noe's movies, especially "Irreversible," or "I Stand Alone." Or even, "In My Skin," directed by Marina de Van. Eye-openers for our American sensitivities.
