I have not tried using Eclipse for Arduino developement, but I do not really believe it's worth it. I believe that using VIM for Arduino developement (which is something I am hoping to try out soon, but I haven't got around to setting everything up yet) might be really beneficial.
The mane benefit with IDEs are:
But since C is not an object oriented language, this feature is not much more useful (arguably less) than the Vims "stupid" autocomplete, which just completes a word when you press a keystroke, without caring if it fits or not.
But this is not supported by the Arduino hardware
Intelligent code refactoring:
But... Vim can do that too, mostly
GIT or another version control:
But... Vim can do that too
Browsing the project tree, managing multiple files:
Arduino project are sparely separated between multiple files, edited by user
All in all: IDE (with a plugin to fix the bug that causes it to NOT behave like Vim) is great for Java or another super high level languages. But for C, Vim is the way to go!