Hmmm, in the System Profiler, check if your SATA bus is clocked at 3 gigabit.
Under Serial-ATA:
If it says 1.5, you need to do a firmware update. If it says 3 gigabit, you need to consult with somebody at Apple. My Aluminum MacBook 2.4ghz was TIMES faster than my White MacBook 2.1ghz in responsiveness.
Under Serial-ATA:

If it says 1.5, you need to do a firmware update. If it says 3 gigabit, you need to consult with somebody at Apple. My Aluminum MacBook 2.4ghz was TIMES faster than my White MacBook 2.1ghz in responsiveness.