I enjoy the variety, every so often getting a wide-open grid like this. Eye-catching to see so much white space — makes for a very neat first impression. A friend of mine (a daily NYT/LAT solver) works at the coffee shop where I write every day, and he mentioned that these types of themeless puzzles are astounding (typically he can't quite finish them, but he enjoys the visual of it all). As Will once mentioned, I wouldn't want to have one of these mega-stacks every week, but once in a while it's a great change of pace.
Making a mega-stack amenable to crossword integration is hard enough in itself — coming up with three (or in this case, four = way harder) grid-spanners which work well enough together to produce clean crossings is very tough. I've tried my hand at it a few times now, just to see how difficult it is, and it's... well, difficult. Every time I think I have something in place, one single crossing will jut out with a strange letter pattern. When I eventually publish a famous book, the main character's name is going to be TKLED.
One aspect I appreciate about MAS's work is that these days, he pushes the envelope past "only" triple and quad stacks. The earliest of the triple-stacks tended to be extremely focused, in that besides the stack(s), there wasn't much else to spruce up the grid. Here's an example from the early days, by... any guesses? Note the differences between this one and today's. Night and day when it comes to the long fill outside the stacks. I really appreciate how MAS integrates MOLTEN LAVA and KITTEN CHOW straight through the quad-stack, and then tosses in LET IT BLEED, LAST HURRAH, ENTRANCE FEES, COAST TO COAST on the periphery. Snappy stuff.
In terms of the usual glue holding together a mega-stack, today's offering is pretty good. A RING is the awkward five-letter partial that jumped out at me, but it's impressive how clean the rest of the crossings are. Well done! So important to choose the right grid-spanners. Speaking of that...
Glad that MAS commented on A TEENAGER IN LOVE already so I don't have to. I've gone back and listened to the song a few times now, and its excessive use in triple stacks... well, I need not say any more. It sure has a nice pattern of semi-alternating consonant-vowel (repeat), so it's understandable. A heavy price to pay, especially since it's been the source of much derision (along with A LOT ON ONES PLATE), but one I thought was reasonable given how much goodness it allowed for.
My favorite clue was [Stream on the side of a mountain, perhaps] which I was convinced would be something esoteric like RILLET. Beautiful misdirection; a stream of MOLTEN LAVA, not water. And finally, one clue that I really liked and didn't want people to miss out on. A HOSTILE TAKEOVER indeed often results in changes across the board, but also often results in changes across the Board (of Directors). A witty double-meaning that tickled me.