I've eaten there twice and found it very underwhelming. Strange monastic feeling dining room, stratospherically expensive wine list, balky service, not fun. And the food? The only dish that I liked was a twee miniature riff on a pastrami sandwich. Otherwise, lots of smoke and mirrors. For the same money, I'd much rather go to L'Astrance or Pierre Gagnaire if I wanted innovative contemporary French haute cuisine.
On the positive side, this Mandarin Oriental seems a tad bit cheaper than the one in London. But since I am no longer on expense account, that seems irrelevant today. The restaurant does offer a lunch prix-fixe for 75 Euros (5 courses). I did see on one of the carte menus a piece of John Dory for 48 Euros. No doubt international businessmen will flock to this hotel as it is cheaper than the Ritz which is just across the street. What a deal.