For the Ashton/Balanchine I have seats in the front row of the Grand Tier boxes, near to the stage but not actually hanging over it: it was the best compromise I could think of between wanting to be close to the Ashton, and wanting a bit of altitude for the Balanchine. Is this a decent idea or a crackpot scheme?
I've tried sitting on many occasions in the side Grand Tier boxes and also the Side Parterre boxes close to the stage and like them a lot. It's imperative that you be in the first row (seats 1-2-3). The second row is unacceptable everywhere in the boxes, mainly because they cram too many chairs into those boxes. I like being close to the stage and you can often see well into the wings, which is fun. You'll almost certainly have a blind corner closest to you, so be prepared for that. But the biggest advantage is just getting a very close-up view of the dancers, which you can't get from the Grand Tier, even in the first row, as it is quite some distance back.
Another little bonus with the Grand Tier boxes: one closest to the stage is the "company box" and the other the "director's box." Dancers from the company sometimes sit in the company box, especially for high-profile performances, and it's fun to see their reaction.
Others can speak to the orchestra. The only times I sit there is for the open rehearsals and I really don't like it. Unless you're lucky enough to be on the aisle in the outside section, you'll have people in front of you, some rather tall and/or sporting big hair that interferes with your view.
Be sure you have printed out the seat diagrams from the on-line ordering site to see exactly where you are.