The IDE I use makes it really easy to develop applications. I am sure that there are others, too, who have already tried it out and sticked to it.
And on top of all, it is free-quality-software. I am most definitely convinced that the open-source community is proud to own such tools.
A little bit about the creation of the IDE: "The Culture of Shipping", the development process that is used to deliver Eclipse is really thought as to create a quality product and to build a community around the product.
Depending on what you are up to, you have many options in tunning it up with plugins that will help you in the development process, besides the great built-in features it has.
Nevertheless, using it to develop enterprise applications with an application server like JBoss, which I don't need to say, open-source as well, enables you to develop quality products, and fulfill the future requirements of todays applications. And getting so far, you can always use Eclipse to debug remotely your application, while you get into a bug.
Technorati tags: Eclipse, JBoss.
