I looked through your shared/util.js and, while I don't want to take anything away from your project, it doesn't seem to me that there is much of a case for significant and useful code sharing in Node. When I think of code sharing, I expect something like Luna, from Asana http://asana.com/luna/

Instead, the examples of shared code in Node are always simple utility functions, validators and the like. While it helps not to have to rewrite those, it's not groundbreaking. Facilitating the sharing of state between client and server -- hopefully irrespective of the server-side language -- would be a much better goal, IMO.