This is a quicky one, due to lack of time.
I tried for the past 24h to install eclipse + pdt on a couple of gentoo boxes I operate for home use. I could describe myself at least as “experienced user“, and yet I couldn’t make it happen the right gentoo way [*]. After spending about 4-5 hours guessing what kind of dependencies should be sufficient to satisfy in order to eventually install the pdt, since the update manager of eclipse [3.2] provided by gentoo stable is a bit old and could not pick them automatically.
Well dudes if you are here in order to install eclipse and pdt on a gentoo system skip the stupid eclipse ebuilds (totally unmaintained maybe?) and go grab eclipse from the source: >>>>> READ HERE AND FOLLOW THE INSTRUCTIONS. IT DEFINATELY WORKS!!!! <<<<<.
Yeah I ebuilded the eclipse from the sources (20 mins - no ccache no distcc, it is java dude 
) in order to have an (obsolete) cvs browser and a C dev platform…. Yeah right…
Conclusion gentoo + eclipse ebuild = bad idea… Do it the Clint Eastwood way: download unpack use…
*The right gentoo way implies the respect to ebuilds and follow the exact instuctions from the official sources/package maintainers etc…