I've used F# at work. It does have a sort-of REPL, you don't have to put one line functions inside a dummy class, and the async monad and queues are pretty han

I've used F# at work. It does have a sort-of REPL, you don't have to put one line functions inside a dummy class, and the async monad and queues are pretty handy. It doesn't benefit from adding yet another set of collection types to the .NET API (which already has two semi-competing sets) but that is unfortunately beneficial, partly due to the next point. The balkanisation between the .NET typesystem (class at a time, overloading ok) and the ML typesystem (sequential and no overloading) is a constant source of irritation. How to make a short name alias to the System.Console.WriteLine variadic function? It's REPL unfortunately doesn't tie into the otherwise impressive VS intellisense and is a pain to attach the debugger to. It hasn't proper closures (you cannot mutate variables you close over). It's not a coherent platform, but a mishmash.