L'Atelier's decor reminds me of haute cuisine restaurants in Paris; a little odd, a little hip, clean, crisp.
The food here is always unique and phenomenal. The plates are physically huge which can be annoying sometimes (the waiter has to clear a landing area on the table in front of you), but the food commands your attention anyway.
The wait staff can be a little cold, but I enjoy the consistency. There's nothing I hate more than returning to a restaurant where I enjoyed the service, only to have a negative experience.
On the downside, a few times they've wanted hefty ($150'ish) deposits upon making reservations on busy nights; I'm not investing on margin here... just trying to eat dinner for crying out loud.
The other negative I'd add is that they pack the tables in on busy/holiday nights (e.g. Valentine's day). What is usually a cozy seating, turns into a sardine can which is hardly romantic.