I saw the show twice at ART, two days in a row, the first time from the back row of the orchestra and the second time from the sunken right. Both were wonderful, though I will admit that I preferred the sunken right, since it most reminded me of the experience of seeing the show off-Broadway. The orchestra view was great, since, as mentioned above, you could see the entire set, but it does feel a bit like watching a show from the outside, while you're in the middle of the show in the sunken pits (Natasha sang "No One Else" basically right to us from a foot away). But then, of course we did have some blocked views in the sunken right, including some of the scenes taking place in the front walkway. The final scene with Natasha and Pierre was visible to us, though.
It seemed to me that the best seats in the house, and the ones likely to be premium if it had been a Broadway house, were the front rows of the orchestra, since they had the best of both worlds: an unobstructed view of most of the scenes, while still feeling pretty immersed in the action. But maybe others will feel otherwise...?