[devongovett]

Yep, this is true. In fact, we already improved performance by over 25x by optimizing algorithms in JavaScript. As covered in the blog post, this rewrite was motivated by more than just performance and does include algorithmic improvements as well. We figured that while we were rewriting we might as well also use a language with more predictable performance traits. But, your points about extensibility does still stand, and that's something we hope to look into more in the future.