I havent done rush in years (as I HATE the rush policy at the Ambassador) so my info might be out of date but as far as I know 8am should be fine. You have to sit in line, unlike the Shubert where you could get a bracelet and come back right before the BO opens.
The seats are partial view, located on the sides of the orchestra. If you get there early enough and are one of the 1st or 2nd seats, rush isnt that bad. Anything beyond that, IMHO isnt worth it.
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