How is it that Python is able to do so many things quickly (even excluding NumPy/SciPy)? Is it more native code libraries? Could Ruby follow this path as effectively?
In general these days, Python "general purpose" code is about as fast/slow as Ruby. And yes, everything that does heavy lifting has native extensions underneath.
Basically, what he found is that for programs that work with large graphs of objects (as opposed to arrays of numbers, which are the domain of numpy and friends), Python isn't all that fast. I don't know how it compares to Ruby though.
I wasn't specifically thinking web frameworks but a number of projects that I found surprising and performant. One example I can recall is Graphite (Whisper, Carbon).