When it came to selecting Node, the biggest benefit was that it was notable. If we had said "HEY we're making another blogging platform in, wait for it, PHP!" -- it would likely have been significantly more difficult that the project would've been seen as noteworthy / attracted any users.
Conversely, Node is not without its drawbacks. The ecosystem is young today. It was positively infantile when we started. I don't even think there was a fully formed RSS library. In fact, from a technical point of view, most of what we've built would have been easier to achieve with other tools and frameworks.
Nowadays when we select technology, we tend to go for the oldest most reliable stuff we can find. The sort of stuff that when you have a problem and you google it, there are 5,000 people who have done it before. Because there are only SO many innovation battles you can fight simultaneously.
At one point we tried to rewrite our infrastructure using Docker/Swarm - it was a 9 month project which ultimately got completely cancelled at the last minute. Why? Turns out Docker Swarm doesn't scale above 500 instances and we needed to run about 10,000 for Ghost(Pro). We asked Docker Inc and their response was pretty much "idk lol". So now, especially with our infrastructure, we almost always select the most tried and tested technology. Boring stuff. Stuff that is very, very well understood.
The problem is, it's not cool to talk about how our infrastructure is built on very straightforward LXC containers, managed by HAProxy, connected to a cluster of MySQL servers. The tech isn't bleeding edge enough to hear about on HN, so you end up not hearing about it. But most of our best tech decisions end up being when we choose older technology.
Sorry, this got really long. Did Node.js influence our success? Yes! It made Ghost more popular and also more difficult to build. Would I change it? Definitely not.