I'm personally using it for a non-web project, but the most typical use case for it is websites where some chunk of logic has to run on both client and server;

I'm personally using it for a non-web project, but the most typical use case for it is websites where some chunk of logic has to run on both client and server; this is quite a common scenario and when it arises, Node is the only game in town unless you want to write that code twice in two different languages and then have to maintain the two versions in lockstep. (People have started using the word 'isomorphic' to describe this scenario; one could argue whether that's strictly accurate, but it's close enough to be suggestive at least.)