If you have a system with 3 GB RAM you can use the following settings to make your STS faster than the default.

STS.ini settings:

-startup
plugins/org.eclipse.equinox.launcher_1.2.0.v20110502.jar
--launcher.library
plugins/org.eclipse.equinox.launcher.win32.win32.x86_1.1.100.v20110502
-product
com.springsource.sts.ide
--launcher.defaultAction
openFile
--launcher.XXMaxPermSize
384M
-vmargs
-Dosgi.requiredJavaVersion=1.5
-Xmn128m
-Xms1024m
-Xmx1024m
-Xss2m
-XX:PermSize=256m
-XX:MaxPermSize=512m
-XX:MaxGCPauseMillis=10
-XX:MaxHeapFreeRatio=50
-XX:+UseConcMarkSweepGC
-XX:+CMSIncrementalMode
-XX:+CMSIncrementalPacing
-XX:+UserParallelGC

JAVA_OPTS environment variable value is -Xms512m -Xmx1g.