The 6.0.2 update to Final Cut Pro seems significant. Apple adds in XDCAM EX, AVC-Intra and AVCHD variants, disk-based HDV, among other things.
Fixes to bugs in rendering and QuickTime gamma display also seem to be included, so the OS X 10.5 shakedown cruise starts. Here's the 6.0.2 Readme.
Update: Apple also released Final Cut Express 4, "a significant upgrade" -- and with a new lower lower price of US$199!
More on FCP... Terence Curren is reporting that the color shift in a Rountrip to Color and back seems fixed; HD4Indies has a rundown of what's new in Final Cut Studio; and The Editblog has good insights on features in FCP updated. Now more Avid-like.
Update 2: Some are having problems with the updated FCP/Leopard/QT (at least with P2 material). A thread on an Apple support forum says Kernel panics on P2 import with 6.0.2 update that could be related to QT 7.3. Obviously, it's best to clone your drive before updating, just in case.
Update 3: Little Frog in Hi-Def notes that FxPlugs can cause P2 import problems in the FCP update.