I have one of the Rev A Macbooks (specs in sig). I upgraded the hard drive to a 160GB 5400rpm drive and have 2 gigs of RAM. Even though my computer is pretty beefy, the computer is pretty slow to start up. If I try to open any apps right after the computer boots up, it will beach ball. The computer is not normal for 2-3 minutes, then everything works normally. I'm only using about half of the HD so I don't know why it's being slow. This only happens when the computer comes out of a cold boot. I always put my computer to sleep, so this doesn't happen very often. I'm running OS X 10.5.1.