Two words: Bru. Tal. That's what this was. It had us on the run right from the start, and though we got the revealer - ALPS (68A: High points of which five are found going up in this puzzle) - somewhat early, and we even noticed the slanted letters A-L-P going up in a few places (and down in one!), it wasn't until the two-hour mark that we finally finished the south-central block and were left with LEG (67A: Long writers' blocks?), that we finally had the big breakthrough. That odd answer, combined with NATION (44A: Baseball, in America), finally did it. We both had wanted NATIONALPASTIME from the get-go, and lo and behold, there it was. All we had to do was climb the Alps to get all the answers we needed. Once you're up there the view is clear, but how exhausting! Hoc opus, hic labor est!
I actually like the trick, now that we finally found it, and ordinarily, I'd love such a clever puzzle, but this one fought us so hard even in the regular fill that I just can't give it a thumbs up. POME (14A: Apple, e.g.) crossing OMAR (6D: Stickup man on "The Wire")?? The M was a guess based solely on the French "pomme," and didn't really feel fair. PAROL (43A: Spoken, as evidence)? Again, sounds vaguely French, but I've never heard it used like that, without an E. ALDOL (51D: Perfume ingredient)? Never heard of it. SELAH (26A: Psalm ender)? Whaa? And finally (I could probably go on, but what's the point?) I only know "Aria da capo" from Bach's Goldberg Variations. It is used when the aria from the head (capo) of the piece returns at the end. I have seen many versions of that work, and never, ever, have I seen the words in the order given in this puzzle. They wouldn't make any sense that way. Order is important in Italian. It's not like Latin. "From the head aria" doesn't mean the same thing as "Aria from the head." It doesn't mean anything! Bah!
I loved the clues on FELON, ATLAS, OOM (pah-pah), and MRED. And the clue for the oft-seen AMATI (15A: Instrument bearing the coat of arms of France's Charles IX) was interesting and completely new to me.
A complex puzzle, and a real challenge, but too much obscure fill soured the thrill of completion. We stared at T_U_ and STE_S for a good twenty minutes before those last two squares finally fell. Again, I say, exhausting. Sometimes Thursdays are more work than Friday and Saturday, it seems. Here's hoping I don't have to eat my words tomorrow.