Great cocktails, but when I was here with a group of friends, we suffered really poor service.
Once you've successfully located the bar (it's not easy as you might think, with just a little brass plaque next to the door to inform you of what lies beyond) and been given the nod of approval from the doorman (also not a small feat), you step into a dimly-lit, but cosy, lounge. You might have to get there early or fight for a seat to perch on because it does get busy, especially on weekends, but once you've got a seat, you can settle yourself in for the night.
The problem I have with it is that you want to feel somehow special for being 'in the know' and rewarded for your hawk-eye tracking skills, and yet you then have to fight an uphill battle against the waitress just for a drink. Half the reason why you are likely to spend a whole evening there is because it takes so bloomin' long to be served.
Go to the Compagnie des Vins Surnaturels or the Curio Parleur instead - both under the same ownership as the Experimental, just with much better service.
37 rue Saint Sauveur, 75002