Well, Eclipse is slow, crashes, has a lot of features but doesn't really do anything nicely (javadoc integration is damn awful tu use). More features doesn't mean better.

What i like about LighTables is that it seems to have few features, but do them well. It has a nice clean UI (even if it's just mockup, i don't think it needs anything else) and the UX seems nice too from what i understood.

Maybe what you didn't understood is that it's NOT an IDE for computer scientists : it's more aimed to visual programmer, webdev, or gamedev, creativecoders. People that want to do both design and coding.

BTW : i just trashed Eclipse, not anyone. I still use it because it's still the best ide for javacoding (even if i haven't done any in a while), which, to me, isn't really flattering for the state of coding IDEs.