In short, equivalent code in node.js and Erlang performed very differently. The node.js used 20% CPU for 2 hours and eventually ran out of memory due to a leak, possibly in the JSON parsing.
To process the same amount of data, the Erlang server used practically no CPU and about 50MB of RAM, with no leaks.
I have no doubt that these sorts of glaring issues will get resolved by the people working on and with node.js, but it's useful to know, if you're planning to build a large-scale product on node.js right now.nod