I downloaded a dozen of my purchased Kindle books to Kindle for Mac.
Of those, half were labelled as having enhanced typesetting on Amazon's website -- though it's possible the versions I received don't include enhanced typesetting code and only devices that can handle enhanced typesetting (PW3, K4iOS, etc.) will receive "enhanced" versions.
Curiously, 2 books showed hyphenation when I opened them in K4Mac. One supposedly had enhanced typesetting,
the other did not. Five other books supposedly having enhanced typesetting did
not have hyphens. Repeat: hyphenation doesn't seem to be reliant on this enhanced typesetting when using K4Mac. After KindleUnpack-ing the books, I noticed that books with hyphenation had CSS for hyphens (i.e., -epub-hyphens:auto; -webkit-hyphens:auto) whereas books without hyphens lacked this CSS. Whether or not the books had enhanced typesetting seemed irrelevant.
I also did a quick comparison of opf files and found no toggle, like there is with TTS. This was disappointing. I was hoping JSWolf was right about a toggle. Though there may still be something in the opf that enables enhanced typesetting that I missed on my cursory scan. There was also nothing in the CSS (other than the hyphen code) that shouted "enhanced typesetting" to me.
I think it's too early to tell what impact this enhanced typesetting will have on Alf, Calibre, KindleUnpack, etc. Hopefully nothing, and I don't expect it to. But the fact that
developers attempting to reverse engineer the enhanced typesetting have been thwarted (so far) worries me.