@evantahler Well: If you install nodejs on a mac these days all you "get" is a command line tool. Don't get me wrong: its cool. But for beginners it is sort of a black box. I think a UI could do following.
1) Offer a tutorial to get started with the first nodejs code
2) Offer a tool / display to set the global npm settings (and show them): npm set / npm get etc.
3) Offer a tool that lists the npm packages (particularly the ones that are often installed with -g) to install them globally (i.e.: coffeescript)
4) Offer a tool where you can add folders as "projects". Every project added has automatic (visual!) checks for the validity of the package.json (Eventually outdated dependency checks) buttons for all the enabled scripts (run/publish/etc.)