I've been meaning to see something at the Four Seasons Centre since it first opened a few years ago; I saw a National Ballet performance there the other weekend. The acoustics are just as good as I had heard. In fact, they're almost too good: even from the mid-to-rear portion of the orchestra level, I could hear the dancer's pointe shoes shuffling and thumping, even during the quieter parts of the music.
(That can spoil the effect--check out the scene in Amadeus when they cut the music from a ballet in one of Mozart's operas to see what I mean.)
The hall itself is laid out as a proper opera house, although the style is decidedly postmodern. The big glass, multi-level atrium works well; the little connecting ramps make it feel detached and separate, but still part of a unified whole. My only beef is that the signage is inadequate for the first-timer--the auditorium entrances are labelled, but they didn't correspond with the seat numbers on my ticket (it would be helpful if the ticket named the nearest entrance).