Apple released their next major operating system Mac OS X 10.5 Leopard today . All macs purchased from today comes pre-installed with Leopard. Leopard comes with more than 300 new features. New features in Leopard are available here.
Final Cut Pro users dont update your system to Leopard. Please wait for the support provided by apple for Apple Pro Apps like Final Cut Studio 2. Avid users never update till you get confirmation from Avid. I will post back when Leopard support for Final Cut Studio and Avid available.
Leopard is available $129 for single user pack or 5 user family pack for $199.