But over the years the architecture has developed real instability. Frequent crashes, terrible and fundamentally broken package/dependency management. Difficult to find features, inconsistent UX and a vast amount of very low-quality plugins in the ecosystem.
Then there's the extremely varied and confusing set of packages. There's even a matrix of packages and features to help you decide! But even that grid barely scratches the surface:
http://www.eclipse.org/downloads/compare.php
Using Eclipse over a period of months creates an ongoing feeling of anxiety and fear of project file corruption. Updating a plugin is a crapshoot. Dead repository links abound, installs and upgrades have a high likelihood of failing. Upgrading Eclipse itself is like playing routlette with your project file.
Two years into using IntelliJ, I'll never look back. I used to be a huge Eclipse fan, used it for many years, but it just hasn't aged well at all -- it's a layered-over Frankenstein that barely resembles its former greatness.