I believe Node.js has solid technical foundations and it will not run into same troubles as Ruby or PHP. There are millions poured into JS research, Ruby never had decent GC or JIT. Also Node.js code base and unit tests are solid, not like client side JS.
Also there are modern strongly typed languages which compile into JS and run just fine on Node.JS. This solves code-base scalability for large teams..
I agree that Node.js is technically solid, but the Ruby/Rails code bases and communities have an immeasurably larger and more mature testing culture than JS/Node... and "modern strongly typed languages compiling to JS" does not by any means solve code-base scalability problems for large teams. That claim is simply false. There are boatloads of experienced Java developers. The people who tend to write "strongly typed languages compiling to JS" tend to write those languages, and not JS.
To be clear: the web would not be what it is without JS, and Node is a fascinating and innovative thing. I disagree that there are loads of people who are experienced in C/C++ are champing at the bit to go write Node. The Java/C# talent pool is massively larger than the non-frontend JS talent pool at this time, and the C/C++ talent pool is largely otherwise occupied. That could change... but it hasn't changed yet. The HN/startup scene is not representative of the software industry at large, and a lot of people writing these "languages that can compile to JS" are part of the industry at large.
All I am saying is that Node.JS has solid foundation to support huge community growth. For me as Java/Scala programmer Node.js is appealing for reasons described above. RoR usually means troubles and I try to avoid it.
Also there are modern strongly typed languages which compile into JS and run just fine on Node.JS. This solves code-base scalability for large teams..