Many people who read about Lisp Machines are not aware that the InterLisp-D worl... | Hacker News

Many people who read about Lisp Machines are not aware that the InterLisp-D world and the MIT world (CADR, LMI, Symbolics etc) had significantly different approaches to how the systems should work, so even if you have read or used the MIT-style systems you will learn a lot by using Medley. I came from MIT out to PARC for a year, and later moved CYC from D machines to Symbolics machines (a complete reimplementation using a different fundamental architecture) so have good experiences with them both.
At heart, the InterLisp language itself isn't that different from MIT lisps, as Interlisp started down the road at BBN and there was a lot of cross fertilization in both directions. And CommonLisp, while heavily based on the "MIT" model has a lot of Interlisp influence in it.