This is an experience, not so much a bar. And most experiences are expensive. The Aviary is an expensive (but worth it) experience.
I'll begin with the visual aspect of The Aviary: it's pretty. The interior is a nice mix of mod & romance...very dim lighting, great art work, orchids. And the seating is either booths with high backs for privacy or benches + chairs at tables. Either option can be construed as intimate.
The cocktails are what you would expect from Grant Achatz and his team of brilliant makers. The drink menu is exceptionally well thought out and well done, and I can only surmise is seasonal. The presentation is a large amount of the fun and intrigue. Lighting drinks on fire, using what I can only describe as a bunson burner under a large carafe of mulling spices, glass canteens that on first inspection look like they house infused olive oil, but in actuality have a spirited spirit in them; it's all very impressive. And everything that I tasted was good. I had a poached pear which tastes like what you would expect, but the pinot noir component was in the form of a hand shaved piece of pinot noir ice. There were walnut crumbles on the rim...bravo.
The service is killer and the point of going is to experience an unconventional, "think about mixology differently" style experience. If that isn't your thing, then this isn't your spot. But it really is a great experience and if you are forward thinking enough to email and get reservations, then enjoy the experience. Worry about the hit to your bank account later.