We're planning to make more "normal" installation scenarios if we see good interest. Using gem was a quick way for us to get the idea out.
I like the idea, and had you not have used Node.js I was going to spend a few hours and create a clone using Node.js since it would be that easy. Mind you not that easy if I were to match your level of service and the site. Hope it has a lot of success.
Node is a network library and you can easily create a TCP server. That s all. On the other hand ruby is great for writing scripts and nice DSLs so the whole concept is implemented very nicely.
On a side note, this reminds me that isaacs (creator of npm) has pushed npm to be for development and not for deploying to end users. Hence using gem instead of npm.