EDIT: For anyone coming to this question through searching, you can install a Gnome Theme called Clearlooks Compact to shorten your tabs in Eclipse. This will free up a
Note: the Default Eclipse 4 just got a bit better with bug 420238 closed:
[CSS] Reduce whitespace usage in the default Eclipse themes
Before:

After:

See Lars Vogel's article about it:
If you fire up the next Eclipse 4.4 milestone build, Eclipse uses much less whitespace and leaves more space for the important content.
(That would be 4.4 M5)
While this is on a technical level a trivial change, I hope that this will improve the initial perception people have in using Eclipse.
A big thanks to Daniel Rolka, Robin Stocker and Dani Megert for doing the majority of the work and a big thanks all involved parties in the Bug report to get this change accepted.