I found the film a bit overwhelming. My initial reaction was muted; through Renn's excellent review, the discussion here, and the friends I saw it with (which I'll get to momentarily), my admiration has grown. In the classic sense of the saying, I can't get the film out of my head.
I do feel it is absolutely a companion piece to The Wrestler, and I felt that way from the first sequence of Nina getting her shoes and feet ready. Where Randy the Ram lived in the gritty reality, this film lives in the mind of Nina. So much so, I was quickly able to pinpoint my initial challenge with the film...navigating the perspectives that the film throws at the viewer, almost continuously and without relief. It was very unsettling (which is the point, of course), and it sort of set me adrift. And as Tyler points out, detached from the protagonist.
In a sense, it works. There cannot be another perspective, because the film is completely in her head, and her life is completely in her art. The off-ramp, so to speak, is years ago in her life. I appreciated seeing this with a dear friend, who studied ballet from ages 4-17, and considerately answered my questions. She was about 20 pounds lighter, which amazes me, because she doesn't carry any spare weight around now (much like Natalie lost 25 pounds, and she started as a waif). She eventually left because she broke both her feet. I asked her about older ballet dancers, and she said many were crippled. There is tremendous beauty in that art, but the price (like professional wrestling) seems to be extraordinarily high. However, more importantly is the psychology of the company and the relationships. It is always about the part. And the person behind you.
Viewed through that prism, I think the film works very well (if also over the top and quite overt). It is dazzlingly intense. It was also quite sensual, and very unsettling (I might have said that already), and I think both represent is the artform.
I think Portman was incredible (as Rourke was before her, and Jackman before him), operating well out of her (or most actresses') comfort zone. She nailed it. The supporting cast was equally game, and provided effective and measured performances for the most part (histrionic when needed).
I'd love to see it again, because I think a second viewing would be very valuable in comprehending the structure and themes.
Exquisite filmmaking, as expected.