I put this on at Bergdorf's on Sunday afternoon and found it fit me almost perfectly. It was comfortable through the shoulders, trim in the waist, and the length (always an issue for me) hit just below waist level.
The blazer is Double-Breasted and with a peak collar, which would normally give it an air of formality. However it is a wool/nylon blend and unstructured, allowing it to form to your body and keeping it a little more casual. I think this adds to the versatility -- dressed up as a great suit, or used as a sweater type layer on weekends.
Mr. Porter is carrying it on their site, where you can see more pics and details.