As I mentioned in the post real bottleneck occurs when it's used with the other supporting libraries (which would be the practical case). Most libraries in Ruby (or Python) are implemented as blocking processes. This defeats the purpose of using an evented programming library.
In contrast, most of the Node.js' libraries are written in a non-blocking manner. This may be because of the initial path the eco-system took. Also JavaScript, being naturally event-driven language encourages writing non-blocking code.
Hello laktek, I really agree about the fact that node.js being from the ground up an evented environment got most libraries written in the same paradigm.
On the other side I fail seeing how Javascript is a more event driven language compared to Ruby. In the context it's often used (the web browser) it supports callbacks, but not with some special semantic. Just callbacks, anonymous functions.
For this point of view I think that languages with coroutines are probably more powerful as event-driven programming languages, because it's possible to save the state across calls in a much more high level way, leading to code resembling a lot erlang code for instance.
In contrast, most of the Node.js' libraries are written in a non-blocking manner. This may be because of the initial path the eco-system took. Also JavaScript, being naturally event-driven language encourages writing non-blocking code.