Il quattro stagioni, as Vivaldi would have it. I love the diagonals, and the six lettered AUTUMN. The semi-revealer in the middle is a nice touch: 35A: Noted quartet (SEASONS). It puts me in mind of a magical evening I spent in April, 1985 at Sainte Chapelle in Paris, listening to the entire Four Seasons. That's over 30 years ago now, but it stays as bright in my memory as anything.
The grid is very nice, in my opinion. Each corner is chunky, with sevens and sixes abounding. What is most interesting is the difficulties that are created by forcing the season names into the diagonal. We get EEEE and IIII (I like the latter much more, because of its clue), not to mention MME, EPEE, and AANDW. I suspect with the progression of natural English spelling on the diagonal, the standard crossword style layering of English is stretched.
I love STRIFE at 1A, an excellent entry to the puzzle, although my first answer entered was the unusual TENTONS. Also nice in that corner is SNUB (27A: Not send an expected invitation, say) and STAIR (31A: It may be a step up).
The NW has the unfortunate ALUMINA and the hitherto unheard acronym OMB (even in its full sense, The Office of Management and Budget doesn't get a lot of press). Furthermore, I like neither the sentiment of 17A, nor the violence associated with it, although the answer GUNBELT is not bad.
I liked the entry into the SW with GUTHRIE, an excellent example of tolerance to oppose to the Texan xenophobic sentiment. I do not like UNRESTS. This is really not an acceptable plural. Would you ever refer to the recent difficulties in various places in the US as the "unrests in Baltimore and Ferguson"? I think not. LADINO is an interesting term which I've seen before, and is apparently extant yet.
The SE is much better. RESPECT, KNOTTY, WILDCAT, DIALECT. SHIRR is a word we only see in the crossword, but the definition is precisely what is given in the clue. AIRACES is a silly bit of nonsense. I do not accept the premise.
Overall, I thought the puzzle solved smoothly, despite the various issues above. I enjoyed it, and kudos to Cece who caught the theme before I did.