I’ve found Eclipse (3.5) runs really slow on Mac in recent releases.
These settings seem to help somewhat. Add/Update them in the eclipse.ini file which can be found in the eclipse package on your mac.
-Dosgi.requiredJavaVersion=1.6
-Xms512m
-Xmx512m
The ‘Dosgi.requiredJavaVersion’ property (set to 1.5 by default), make sure Java 1.6 is used. The other settings set the memory allocation – make these more if Eclipse is still running slow.