I couldn't tell you why, but reading code feels much, much more natural with it than with most other fonts.
Perhaps it's the high degree of separation because every character looks meaningfully different?
The "kerning" (or whatever the visual space between letters is called in monospace fonts) is also among the best.
Ah, thanks for that. I wasn't brave enough! I was using the Duotone version (normal version is Linear, while italics and bold are Casual). Indeed I'm happier with everything being Casual.
You'll find it more accessible via METAPOST, and there have been font designs made using it. Better starting link is:
https://davidcarlisle.github.io/uk-tex-faq/FAQ-mfptutorials....
Prof. Hermann Zapf's eponymous Zapfino has the latter --- I even included an animation of it in my paper on it:
It was a fun paper to write, but came a bit too late to have any influence --- at the same conference Jonathan Kew presented XeTeX and shortly thereafter luatex was developed, so it ceased to be necessary to stitch together hundreds of .eps files to make a possibly several GB PostScript file which then had to be distilled to a PDF using the commercial Adobe Acrobat.