In addition to the MacOs X 10.4.2 updater, over at www.apple.com/finalcutstudio/downloads. you can download updates to all the Final Cut Studio applications.
Some of them look like complete replacements. Have a blast!
If anybody can find a doc on what this upgrade fixes (besides "improved reliability" let us know. We do know that it fixes the third party plug in problem but that's about it.