Wow, I'm really happy with Eclipse. I was using IntelliJ before, and though I liked it, it was somewhat slow on my system. Also, I wasn't actually a paying customer, so I felt bad - not so bad as to pony up $400 for a licensed copy, but bad enough. Using Eclipse I'm much happier, both from a development and moral standpoint (i.e. I'm not ripping off another software developer).
That said, the reason why I'm so happy with Eclipse is it's awesome for our project at work. I haven't gotten used to using it at home because my development is mostly for JSP and the size of my personal projects are considerably smaller. However, here at work (I'm here now), the project is much bigger with a variety of files, APIs, etc. I'm constantly managing changes from CVS and doing builds using Ant - both integrated features in Eclipse. Today I ran across the local history window and was estatic! What a great feature! CVS is the main reason I'm so happy, though... The integration is just really well done - better than any other app I've tried including IntelliJ. I'm a command-line CVSer... I usually poo-poo UIs as fluff. But being able to do all the updating, syching, checking history and tags via the interface is awesome. I love having almost everything except my local app server running under one app.
My one main problem with Eclipse is that any file you want to edit has to be part of a project. That's a pain, and I end up having to swap to UltraEdit for a variety of little files that you always end up having to view during development. I don't see why I can't just open some random file - even if it's just in the plain-text editor. I can't believe I'm the only person with this problem, so maybe they'll change it in the next big version.
Anyways, after a day or so getting used to the app, I'm now MUCH more productive than I was before with a better understanding of the project as a whole. That's awesome. Well worth the transition effort.