> Non-string values are not valid hash keys. - ES6 Maps
Yes, this is a good thing :)
> The prototype system is less powerful .. - No. Just different
Javascript let you use prototypes to cause map lookups for absent keys to fall back to a different map. Lua lets you use prototypes to override every operator, make the object callable, override map lookups for absent keys, and override assignment of new keys. All of these operations can be made to call into arbitrary functions the user provides. Python, an OO scripting language, provides all of the same features.
It seems to me that among these three languages there is a greater difference between the more powerful systems and the less powerful system than between the prototypal systems and the OO system.
> The language will never have continuations.. - Generators help here. We use them with node --harmony
Python also has generators, but you still need greenlet or stackless if you want to use coroutines. The inability to suspend from a subroutine is a deal breaker. Generators are probably nice for writing generators. For writing control flow, Continuation.js seems like a better choice.
> Scoping. - Fat arrows and block scoping coming in ES6.
=> lets you use a lexically scoped this, which is likely a dynamically scoped this from an enclosing lexical scope. This sounds useful, but it doesn't really make things less messy.