There's not exactly a lot to say about this lens. The only word I can think of to express myself is: Superb. Yes, it's expensive. Yes, it's heavy. No, it's not the fastest focusing lens out there but image quality is really first rate. And it's very fast being an f1.2 lens.
The following images were taken in a really dark environment with only some small spotlights inside where the birds resided. I hope the images will give you an idea of what to expect with this lens. Like the Olympus 75 f1.8 it is one of the sharpest lenses I have ever used. Very difficult to select which is the sharpest but we are talking very different focal lengths here and they would be used for differing purposes.
But one thing I can safely say, I'm really privileged to own both lenses.