Andy Keep has given many talks on the nanopass compiler, and searching for him on YouTube will give you lots of interesting talks!
Chez, together with the commercial lisps, is among the best dynamic language systems there are. Apart from the unboxed floats me ruined by another sibling posts, it produces really good code.
In my tests it has been ever so slightly faster than sbcl when the code does not depend excessively on spending time in the standard library. SBCL's standard library has had a lot more optimization work done on the individual function level (I'm looking at you, isqrt). Most of the difference in my case can be erased by the new SBCL block optimization though, which chez does on the module level.
It really cool to see a little used lisp have such a great impact.
[1] https://news.ycombinator.com/item?id=15156027
[2] https://blog.racket-lang.org/2020/02/racket-on-chez-status.h...