Parrot's been claiming that it's slow and incomplete now, but a solution to that is just around the corner for a few years.

Maybe that's true, but I think that'd be the main concern of any compiler writer thinking of targeting it. It's not a mature platform with known pros and cons, unlike the JVM or LLVM.

I hope it all turns out for the best and Parrot delivers on its promises. But I can see why e.g. the PHP team isn't rushing to target it given the state of its native languages.