[knhung]

The idea it's good but hard to make it good. A universal language is hard to optimise for a particular language.

[nine_k]

The point, AFAICT, is not in using all capabilities of all the target languages. Rather, it's about expressing some narrower class of computations and grafting them seamlessly into the target languages. Think of data formats, parsers, network protocols, stuff like handling and rendering of text, etc.