I saw a talk about node.js by Mike Amundsen the other day - he did all his work using http://c9.io/ etc The IDE seemed a bit flaky, but quite powerful - the concept certainly seems promising. http://www.amundsen.com

Having said that, for me personally I still prefer a very responsive UI, lots of keyboard shortcuts, and the kind of workspace / UI customization you can only get from desktops nowadays.