Alinea is hereby thirded. Our last meal there was last Thanksgiving, and we are still talking about it. SO, if money* and time** are no object, then yup, that's the one restaurant to visit.
BUT if you're looking for something that's quite nice, yet a little less of a commitment, and also near-ish to downtown, might i suggest something selected from the trio of Blackbird, Naha, or North Pond? I've had some fun meals at Graham Elliot as well.
You might also consider rolling the dice and seeing if you can get a reservation at Schwa. Really amazing creative food served to you by the 4 chefs in a tiny little storefront. Ring them in the late-ish afternoon and perhaps you'll get lucky.
All these restaurants are well-discussed here on the board - search is your friend. You can do a search on the googles like:
Blackbird site:lthforum.com
good luck and good eating
-erb
*you'll likely drop $400 a head, at the inside.
**and spend 4-5 hours.