EclipseOn Mac OS X
EclipseFP seems to work ok on Mac_OS_X, but it doesn't seem like there is much testing on OS X. Installing per instructions will get you editing and building pretty quickly.
However, getting syntax highlighting working doesn't work on 2.2 (feb 2012). If you actually manage to get scion-browser and build wrapper compiled, then your code will probably stop compiling in the IDE. So just live without those features for now or you can burn a lot of time.
In the meantime, you get good edit/compile/build with EclipseFP 2.2.2.
These instructions are applicable to EclipseFp 2.2.2 and Lion, and probably apply to other versions of OS X and EclipseFP.