> > I was checking some CLR opinions and - correct me please if I'm wrong - seems
> > that there were some trouble with continuations.

On the CLR front (and I'm pretty sure on the JVM front as well) continuations pose a very major problem for implementers. It's a difficult problem to solve while preserving decent performance characteristics. And the approaches that have been attempted in the past (like exploiting the exception facilities of the runtime) don't hold forth the promise of future performance improvements.

This is one of those things that we'll need to solve as a community for defining what Ruby is and isn't.

-John