My experience with heavily metaprogrammed Ruby is that this story has a dark side. Yes, when language and program fit one another well, you end up with code which is clear, small, and efficient. That is true... until you need to add a new feature that was not accounted for in the language design. Now you have to wade into the code of the "compiler".

Abstraction generally gives up flexibility to obtain conciseness. Certainly a balance must be struck, but "not flexible enough" has caused me vastly more pain than "not concise enough". As a consultant who frequently wades into other people's code, I generally consider metaprogramming to be a scourge.