Twelve-letter answers are the bane of themeless constructors (along with 13s and 14s). Black squares are so precious in themelesses, and when you have to deploy six of them immediately, you sacrifice flexibility from the get-go.
Love DUMPSTER FIRE and VITRUVIAN MAN! (I built a themeless around VITRUVIAN MAN years ago, but I had so much trouble with the grid that I abandoned it. Stupid 12-letter entries.)

Another grid design element of note today: the big upper right and lower left corners. It's rare for constructors to try anything quad-stacked, even eight-letter answers, because they're so darn hard to make both smooth and sizzling. I thought Pavel did a nice job getting both of these relatively smooth — just STE and ACAN as prices to pay — but neither corner shined for me. I do like HABANEROs and IN STEREO, but nothing else stood out.
A common issue for these big quad-stacks; you tend to either get smooth or sizzling, but not both.
As a huge fan of John Nash, I loved GAME THEORY in the bottom stack. ARE WE ALONE was nice too, at least for us cosmic ponderers. There were some prices to pay in AGAS and ETERNE, but I enjoyed GAME THEORY so much that this corner would have turned out great in my eyes …
… except that I had already experienced ETOILE in the upper left corner. ETOILE (deep French) and ETERNE (only in poetry) aren't exactly related, but they felt like similar enough dabs of crossword glue — containing so many friendly letters for constructors — that having both didn't seem elegant. Ah well. GAME THEORY is still a game-changing entry for this solver.
TITRATOR … back in my day, we had to do all our titrations by hand. You kids have it easy with your mechanical TITRATORs, grumble grumble.
Overall, there was too much crossword glue for my taste — along with the aforementioned, there was ECU / SESS, TO TEN, the dreaded arbitrary EEE shoe spec, OLEO / KIP etc. (Though as a huge "Princess Bride" fan, I don't mind INIGO at all!) But that's one of the side effects of featuring 12-letter entries. Rarely easy, as those buggers can propagate problems all throughout a grid.