Indeed it is definitely the week for updates! Along with firmware and software updates for other Apple products (not to mention other products as well, like Office and Chrome), Apple has issued a fix for the ongoing audio issues that early 2009 model Mac Pro users have been experiencing.
Many users have noticed that when running Snow Leopard (particularly OS X 10.6.2) that certain audio processing activities caused an extraordinary amount of processor utilization. We recently posted a small article regarding rumor that Apple wasand it looks like the rumor was true.
Be sure to run a full backup on your system before applying the update.
If you have not experienced problems with high CPU usage when running audio applications on your Mac Pro, you do not need to install this update; however, it should not hurt to do so. Additionally, future updates from Apple may include this fix, so eventually you will more than likely have it applied one way or another.