I've had some experiences where it really helped. My supervisor uses a teaching stack based VM for his compilers class - it is slow as all hell but very simple,

I've had some experiences where it really helped. My supervisor uses a teaching stack based VM for his compilers class - it is slow as all hell but very simple, easy to get running, and it gives very good debugging info. Similarly, I can see the value in a simplified graphics API that let's you focus on the basic theory, or a simplified language with Hoare logic for writing loop invariants in an algorithms class.