This is a really good summary, thank you for posting. Gives me a better understanding of various tradeoffs made.

I would certainly like to see lightweight threads on top of the posix/win32 threads (eg like in Erlang or the new Java Loom). They enable a particular programming pattern that allows to wrap a function call in a ‘thread spawn’ (it seems that Nim already optimizes copy across threads) – making the whole programming model more multi-core friendly