Very long back, puffy pasterns, upright shoulder. Toes out in front, but straight in the back. Decent set to his hocks, neck looks nice but set high on his shoulders. Reasonable heartgirth, nice horse overall.
I agree with waresbear except on one part - the back. He does have a long back, don't get me wrong, but I wouldn't call it a -very- long back. Very implies extremely and this isn't to that degree. My gelding is longer, juuuuuust edging into what I would call very long:
I honestly think his long back comes with his breeding. He is built more as a racehorse than anything, all the quarter horses I've seen are more bulky. When he runs, he stretches like a racehorse. You would expect him to be trained for racing, not a small western pleasure horse.
One thing I learned is to judge the horse as a whole. I believe if he had a short back, he would be awkward.