Since this is HN, I want to point out that they use Common Lisp and are a productive contributor to the CL community with open source. Congratulations!
For new hires, the fact is, a quantum computing codebase is daunting to learn regardless of the language. Therefore, apprenticing someone on a new language at the same time as everything else they are learning is not really the same relative burden that it would be if, say, the application was a plain boring database CRUD app in an unfamiliar language.
We definitely make excellent use of macros and DSLs and the REPL in many ways. I wish I could talk about it more, but alas.