"To change one color throughout the entire Groupon.com webpage, that was estimated to take three months to do".
... It seems that they rewrite from scratch a terrible mess, the switch to Node is anecdotical
"It took three months just to change the color appearing across the website, he said. “After we moved to Node.js, it took us literally a week.”" - http://www.datacenterknowledge.com/archives/2013/12/04/paypa...
The problem is devs using it for every use cases,even when it doesnt make sense, just like rails.
Of course,in a few years you'll read articles about how bad node is, just because developpers did not choose the right tool for the job.