Preferably an IDE. Integrated support for Subversion/Git is a big plus as we are a group of 6 people working.
Vim/Emacs is not that pop
You should try Aptana or WebStorm, the second one is not free, but worth the required value. WebStorm has a default Node.JS and Express project available. If you select to a new project you can start one with these options as well. The IDE has some nice code completion, good highlighting and a large group of addons to enhance your experience with a lot of new technology.