Apple describes the problem as:
MacBook Pro Hard Drive Firmware Update 2.0 reduces certain infrequent noises made by 7200-rpm drives.
These drives shipped with the June 2009 MacBook Pro.
To complete the firmware update process, please follow the instructions in the updater application (/Applications/Utilities/Hard Drive Update.app).
The updater will launch automatically when the installation is complete.
New Hard Drive firmware will be: 0007APM2
This supposedly only affected 500GB 7200RPM 2.5" SATA Hard Drives manufactured for Apple by Seagate.
My personal experience with Seagate hard drives is very poor. I have had nearly every hard drive I've ever owned (Seagate or Seagate OEM) fail.
Apple also posted a Bluetooth firmware update:
Apple Bluetooth Firmware Update
Your Mac must have Bluetooth 2.0 or 2.1 - which is most Macs from 2006 -2009
This update helped my connection to be more stable with a lot of things (IE my mouse and printer) ... but oddly broke support for bluetooth tethering.