Bentley's is the quintessential fancy pants special occasion spot and they do it well. A reservation is an absolute must and be sure to request a table near a window for really spectacular dining views.
I've been for dinner, drinks, and lunch. Getting drinks at the bar is the one thing I wouldn't recommend, unless you're just waiting on a table. The bar area is generally devoid of people, has a strange assortment of furniture, and the bartender isn't exactly attentive.
The food: the plaza salmon, filet, salads, and soups are all delish. The grown up mac and cheese is good, but over-hyped and far too rich.