> No JS JIT, only interpreter. I don’t care that much about JS performance as a user and the difference in complexity is astounding.

One of the cool techniques we used in earlier versions of JSC (although someone told me it's been dialed back since then) was caching property accesses / method calls in the bytecode interpreter. This technique ended up getting published by someone else in a different context:

https://web.cs.upb.de/cp/download.py?key=ecoop10

I think there's more to be explored along these lines.