It sounds a bit like you guys rewrote it because node.js is hot and you then stuck with the rewrite because of sunk costs. Or am I imagining things?
Thanks for sharing your experiences with us. I'm just asking those questions because I want to learn more about them.
The article might as well be written as "we refactored our code and got a nice speed boost".
Most of node modules are still in active development. As I've stated in the blog post, that's a pro and con, but we estimated that the pro was greater than the con :)
Couldn't you rewrite for ease the maintenance in ruby?