I took a brief look at these things, and my impression is that their stuff isn't "ready" for anyone outside Jane Street, even though they put a lot of effort in building the ecosystem and open source their code.
I've used some of their other libraries too, their logging and unit test ppx are common maybe even de facto standards as much as the ocaml world has such a thing. I've also used, off the top of my head, their code formatter, one of their test frameworks, their implementations of some advanced data structures.
Sometimes you do run into one like the other commenter said, where that shit just does not work. It depends on an undocumented something they shipped separately, or needs a secret bit of config or whatever. These aren't malicious, I open a ticket and come back in a year or two often they'll be working.
It's not zero frustration but I appreciate their approach of just throwing everything over rather than spending more resources testing and polishing fewer releases. Their code quality is generally very high and even if I can't get something working directly, it provides a rigorous & vetted example implementation.
How is the design of the APIs? How stable are they?
Does Jane Street respond to bug reports/pull requests (if any) quickly?
I worked on Bloomberg DLIB which is basically an implementation of https://www.cs.tufts.edu/~nr/cs257/archive/simon-peyton-jone...
I love Lean 4, but good luck getting help with it from AI. Today's project-in-progress is digesting their reference manual to fit well within a 200K context window. We'll see if that helps.