Yesterday I installed my new 500GB Seagate Momentus XT Hybrid hard drive in my 2009 Unibody MacBook to replace the OEM 160GB hard drive. So far I'm impressed. Everything seems to open more quickly and the boot time have been cut in half after a few cycles. The drive is very quiet, which surprises me since I read somewhere these were a bit noisy - not this one. It is a 7200RPM drive with 32MB regular cache, which already makes it a nice drive. But it's the 4GB of smart Flash memory attached that allows it "remember" what files are opened frequently and puts that stuff in flash (that's why it now boots so much faster). Anyway, it's too early to tell my overall impressions, but so far I'm impressed and happy I spent a little extra for the hybrid version.