Re: Anything we should steal ? - Definitely
I thought that the compiler was (eventually) written in PL/1. (It used to be called NPL for New Programming Language until the National Physics Labs complained.) Wherever the compiler was slow they optimized the compiler so things got better and better. There was a compiler switch for generating optimized code but they discovered that compilation times were faster with optimization enables so they removed the compiler switch and made all compilations optimized. The only code not in PL/1 were device drivers and bootstraps etc.
There was an early decision to do all of the code in PL/1. They figured that they would lose a factor of 2 by not being in assembly but gain an order of magnitude by being able to manage the code base. Best decision - every time someone complained about slow generated code they fixed the compiler and everyone benefited.
We stole the hierarchical file system for the Dartmouth Time Sharing System. We didn't have hardware for paging so we couldn't steal their memory system.
MULTICS was a great system before its time.