Netbeans has very good JavaScript support and in browser JavaScript debugging. It is the only one I know of so far that does in-browser debugging. VS and IE do but IE's debugger is primitive. Netbeans allows you to debug and trace through the entire stack in one location. I went through a lot of them Aptana, Eclipse, et. al. and found that Netbeans provided the best JavaScript development tools in my opinion.
Where applicable, I use MS Visual Studio - applies "intellisense" to your JavaScript code and supports "step though" code debugging with access to variable values.