Well, good for them for choosing a technology that they enjoy and making it work. There's more than enough room for another mature application platform.
We've done literally no tuning as well. It's all out of box. It just sucks up the requests and spits them out with a smile.
Still by reading the article I still don't see how moving to another framework + platform made it better. Maybe our case is so very different.
I have considered the move for quite a while, every time I run the performance tests, .Net comes faster.
Maintainability wise, it is still easier to manage .Net applications than NodeJS. The tooling for testing (and not just Unit Testing) is abundant and mature.
Cost savings are also debatable. In our case, we measure Infrastructure Costs + Maintenance Costs, and windows is way cheaper putting the two together. Now, they are using a PaaS, so that might make it worth while. For us a PaaS is really not an option since we need a lot more control.
I do agree with the mongoDB choice. I love Mongodb. We us eMongoDB. But we have so many problems because it never reclaims deleted data. The size just grows. And that is maintenance hell. We are analyzing potential replacements.
For us, NodeJS still doesn't have that much to offer. :D So we are sticking with .Net.
I have started running some stuff under mono though!
(I was replaying to benologist's comment, but there's a bug in HN system)
For example, the 'official' WebSocket support (SignalR):
> Please support .NET 3.5 Please
> Of course it's technically possible, but it's not a goal.