Apple Performance Update 1.0 is on Software Update
There's been a problem with the 500GB drives in Unibody MacBook Pros where there's a hardware delay due to the drive and the machine not quite understanding the spin-down and spin-up cycles. Well... this is the second update I know of for the MBP to try and fix this. I haven't seen it, but I'll certainly update on the off-chance that I have seen it and just not noticed it. That would be a funny one.