Bishop Williamson has praised Poem of the Mangod before. It was years ago and, I think, while he was in Argentina and before he was ever ordered to shut down his weekly newsletter. There was, at the time, a lot of chatter on email forums about the poem.
Frankly, the only person I have respect for that ever praised Poem of the Mangod is Bishop Williamson.
However, I have not read it nor do I plan to read it, not just because he is in the minority, but because the other people who were praising it were radical Modernists and John Paul 2 fantatics. (Though I was absolutely not sedevacantist at the time, I was absolutely certain that John Paul was not "Great".)