Well, at first, I thought this was a silly idea, because once you get the trick, the two sides can be solved almost simultaneously, but we got mired, as you maybe did too, in the SE. I thought that I was so clever by entering "nothing" in for 65A, but it didn't work out the way I thought it should. Finally, Frannie said "It's like it shouldn't even exist at all," and bingo, we were done. I tried getting the puzzle to "check" with empty boxes, but that didn't work, so I put in Xs, and that did.
Overall, the last little gimmick saved this one for me. It's a nice Halloween-y theme, but as stated already, it played a little easy. And there's been so much backward stuff lately. None, none, none, and then all the time. I'm not complaining, but it just seems a little odd.
15A: Not yet delivered (INUTERO) was a nice way to clue that, and I don't think I've ever heard the term 23A: Clusterfist (MISER) before, so that was interesting. Also, I love seeing JSBACH (35A: "St. Matthew Passion" composer, for short) in the grid. Ahhh... Bach...
Lastly, is MITTENS really a 10D: Nickname for a 2012 presidential candidate? I thought that was just our pet name for him!