If you always want your Mac to be fully updated than hit up software update. 10.6.4 is available to everyone now.

Some new things:

* resolve an issue that causes the keyboard or trackpad to become unresponsive
* resolve an issue that may prevent some Adobe Creative Suite 3 applications from opening
* address issues copying, renaming, or deleting files on SMB file servers
* improve reliability of VPN connections
* resolve a playback issue in DVD Player when using Good Quality deinterlacing
* resolve an issue editing photos with iPhoto or Aperture in full screen view
* improve compatibility with some braille displays

You can find out more about the update here and here.