I recently bought a MacBook Pro (2 GHz Intel Core i7 with 64-bit kernel and extensions enabled) to develop with Java. First thing to do was updating Java and installing Eclipse IDE, but everything about Eclipse was very slow.
So I started googling and found the solution here:
The problem was related to 64-bit, Java and Eclipse are ready for working on 64-bit but you have to configure them.
Then, open eclipse.ini and update of this way (lines updated are 12, 16, 19, 20 and 21):
-startup ../../../plugins/org.eclipse.equinox.launcher_1.1.1.R36x_v20101122_1400.jar --launcher.library ../../../plugins/org.eclipse.equinox.launcher.cocoa.macosx.x86_64_1.1.2.R36x_v20101019_1345 -product org.eclipse.epp.package.jee.product --launcher.defaultAction openFile -showsplash org.eclipse.platform --launcher.XXMaxPermSize 512m --launcher.defaultAction openFile -vmargs -Dosgi.requiredJavaVersion=1.6 -XstartOnFirstThread -Dorg.eclipse.swt.internal.carbon.smallFonts -XX:MaxPermSize=512m -Xms80m -Xmx1024m -Xdock:icon=../Resources/Eclipse.icns -XstartOnFirstThread -Dorg.eclipse.swt.internal.carbon.smallFonts