[rch]

I tried, but couldn't make it through.

Here's an approximate quote from about 25 minutes in (on mobile clients):

"between latency, long connection, disconnects, just incomplete socket transactions are not very polite in terms of how TCP is being used so you don't always get your heartbeat or your acknowledgement or the termination of the connection. And so it really creates a lot of stress on your servers because they end up with quite a lot of crap that they have to maintain. And Node does a really great job of doing it all for you."

To be fair, he does go on to explain some of what it doesn't do for you though.