I'm going to Paris in May, and not going single for the first time in a long while :-)
We're planning a great meal, and I was thinking about L'Ambroisie, it is in a great area to walk in and out even in less than ideal weather because of the covered alleys.
My girlfriend eat pretty much everything except seafood (outside of salmon and other "regular" fish); so having a great menu with a more "meat centric" selection.
I am also looking at Lasserre and Ledoyen (both are near nice areas, and close to L'Orangerie).
I was also looking at Le Pré Catelan, but since it is a bit further away it is "less fun" to walk in and walk out for a stroll after lunch or dinner (need to taxi in and out).
Le Cinq will be kept as a backup (mostly because it has a easier menu ?).
(I'd like to go back to Gagnaire, but it might be too "exotic")