I love good IDE's.
One of the reason's I love eclipse is because it is so versatile. You can add any type of addin to Eclipse, and there are many out there. Today I wish to talk a little about APTANA IDE.
It allows you to use code-Assist, or as Microsoft users call it "intellisense". You can add your own libraries to the code assist area, and it considers them part of the framework.
It works with CSS, HTML, JS, RUBY, RHTML, RAILS.
It's pretty easy to use with Microsoft's excellent Ajax Framework (formerly known as atlas).
It's still not as god as microsoft's Visual Studio 2005 IDE. check out the free version
Microsoft Web Developer Express
They work well together, and do not step on each others toes.
give them a try.