Sun has just released Java SE 6 Update 14 with some great performance improvements.

• Optimization Using Escape Analysis : [-XX:+DoEscapeAnalysis]
  HotSpot will look for objects that are created and reference by a single thread and omit allocation treating them like local variables.
• Compressed Object Pointers : [-XX:+UseCompressedOops]
  Improves 64-bit JRE performance by compressing object references to 32 bits when the object heap is less than 32 GB.
• Garbage First (G1) Garbage Collector : [-XX:+UnlockExperimentalVMOptions -XX:+UseG1GC]
  A low pause, server style collector that is more predictable.
• Improved TreeMap Iteration : [-XX:+AggressiveOpts]
  Improved iteration for frequent passes over TreeMaps when the option is turned on.

Release notes indicate though that to use the G1 garbage collector in production, a Java support contract must have been purchased. I guess Oracle is starting to make its mark on Sun.