Happy St. Patrick's Day! I hope everything has been green for you.
I did not have much difficulty with this puzzle at all. It helped that I had put in OPENTABLE as my first entry at 5D: Restaurant availability. I would have liked a reference to the app, and I suspect that was how it was clued initially. So when I was working the acrosses in that corner and came to 17A: Like many disasters, in hindsight, I thought, well, that should be "preventable". And indeed it was.
I found the other answers that turn corners mostly by process of elimination. I like that they are not symmetrically placed, so their discovery was part of the fun. I did not get the point, even after the revealer, until I had finished the puzzle and looked it over. See, each one has "event" at the corner, so they are an example of TURNOFEV[ENTS]. I like that one answer turns at V, one at E, and one at N. Unfortunately, the revealer also turns at E, so not as smooth as I'd like.
Other than the theme, the puzzle is really pretty good. I don't love VAR crossing AMT, and the NE and SW corners are all 3-letter answers. But you get a large number of really nice answers in exchange.
20A: Devilish sorts? (SATANISTS) is fine. 34D: Act out (DRAMATIZE), very good. 18A: Without consideration (UNADVISED). NBADRAFT. NESTEGGS. There is a muchness of goodness.
1A: Sauce for linguine (PESTO) - well, I do enjoy pesto. But I'm just not convinced that it's a common sauce for linguine. My first thought for that particular pasta is clams, and in fact that's what googles best. I'm giving this a C+.