We love the 5th Avenue. They get a great array of Broadway shows and everything I've seen here has been top-rate. (Recent shows include A Chorus Line and Les Miserables.)
The atmosphere of the theatre is cozy and warm. It feels very "old world" with the rich mouldings and dark wood everywhere, but I have to agree with the previous poster who mentioned that the illusion is lost when so many theatre-goers arrive in their jeans, sweatshirts and docs. It is really *that* much trouble to "dress" for the theatre? I really wish we in Seattle could "get" that there are (or should be) different levels of dress for different venues and activies.