Check out WebStorm 8 integration: lots of new features and fixed bugs, significant performance and usability improvements
You can also try standalone web UI version () (please note that the WebStorm version is far more stable and production ready, while the web UI version is more like a preview and not actively maintained at the moment)
Ever spent several minutes trying to reproduce some bug and then realised that you didn't set required breakpoint? Tired of stepping into minified jQuery? spy-js allows you to select only scripts and events you're interested in, run your scenario and then inspect collected runtime data like function parameters, return values and exceptions to make your debugging easier.