A tricky Thursday from Mr. Chen! From what I've pieced together, he's something of a math/science/engineering sort of fellow, so it seems right up his alley to build a puzzle around square roots. And how beautifully done! The last one I got was the first in the sequence, and the funniest, because it's the same! HOLEINONE (17A: Ace) is the same whether you square the one or not. The others, though, progress up to four. FANTASTICTWO (28A: Marvel Comics group), ONCLOUDTHREE (45A: Elated), and SWEETFOUR (60A: Milestone birthday). It's a little unfortunate that a note was required (in the online version anyway... did anyone see it in the actual paper?), but even so, I'm still giving the theme an A. It's just so cleanly done.
1A: Loads (RAFTS) is kind of dull, but the words can be quite different, so that's a nice juxtaposition. B-
And my favorite clue answer: 2D: "Hi, Ho!" (ALOHA) because it totally got me, even after yesterday's "HI hi." I don't know what I was looking for, but I laughed out loud when I realized what it was.
The fill is relatively clean, too, apart from a few groaners like FILER and SUI. NOUNS (18D: Words ending in "o" in Esperanto) was interesting, I enjoyed BARACUS and ATEAM, and contrasting that lowbrow pair, we have AMBITS (32A: Circuits), CITADEL (27D: Bulwark), and ADHERE (44A: Accrete) which are all quite erudite. The long downs are all solid, and we get the entire name of LAOTSE. It's just one variant of his name, but still, I'll take it.
My error sadly came at PECOS (26A: River mentioned in Yosemite Sam's self-introduction). I must have put in NITS (22D: Snags) without really thinking it over and I never went back. Which brings me to my last topic - the online version of the puzzle now leaves my error square unfilled, forever exposing my shame. I like the change, actually, and I think it might make me a little more careful. That's the dream anyway. We'll see if it works.
Solid Thursday - even without a rebus.
p.s. TOM gets in for a second day in a row!