Coutume is something of an old hand in the (relatively new) Parisian third-wave coffee scene. On the left bank, on the relatively untrodden (by tourists, at least) rue de Babylone, it is both a roaster (which supplies the likes of Black Market) and a café in its own right. Of the three third-wave cafés I visited on my trip to Paris in May, character-wise it sits between Ten Belles, which felt as if it had been lifted straight out of Soho, and Black Market, which felt like a little French café/bar.
On the one hand, Coutume felt undeniably French, particular since it was the only one of the three to offer table service. It also seemed to have the most local custom. On the other hand, if I closed my ears and took down the menus, it too could have been lifted straight out of Soho, with its tiled counters and bare, undecorated walls.
Not that this is any criticism; of the three, I preferred the coffee at Coutume, although it was a close-run thing with Black Market. I also loved the atmosphere, it being a great place to drink great coffee.
August 2014: you can see what I made of Coutume on my return visit in 2014.