If I remember the discussion correctly, it seemed to center on the node code still being very slow despite being faster than the java system it replaced.
People commented that the increase in speed may of simply been due to the act of rewriting the system and not being tied down by in house framework rather than any favorable property of node.js
I don't see why you would expect node.js to be faster than anything else; despite all the time that's been poured into it I'd think JavaScript is still inherently difficult to optimize (and I'd guess they also need to do a lot of extra work to deal with numbers in the proper precision since they are handling money).
