I have used the commercial version of Litespeed a few times, quite impressive, featureful and fast, but configuration and management was a PITA.

exactly. that was the same for me, "what the heck is litespeed?!" was my reaction, then i noticed it's been there for a few years already.

and the fact that it's a drop-in replacement for apache config files is just mind-boggling. who in their sane mind would want to reproduce that complexity?

I'd never heard until Life speed until today. I wonder if it's one or a few major players using it?

I heard its name frequently around the time before nginx came to its fame. Maybe 15 years ago. However, I never heard any major players use it after that.