Installed 6 hour ago on my powerbook G4 1.3.
Everithing is ok. Common applications like Adobe CS Suite, Macromedia Studio and similar work without any problem (so far).
The new mail is great... it was nice to have same interface implemented also in other aplication.
Spotlight work very well. You just have to wait 30-40 minutes after installing OS for first time indexing.
The only problem I have found is with PGPMail. Just uninstalled it in the hope o a new compatible version soon.
I have the impression that some applications lunch faster.
No other perceptible speed inprovment on the standard system operation. Havn't find a way for now to test OpenGL performance and other stuff.
Safari RSS work very well. I'ts simple and fast.
I have also repaired my permission with disk utils and it was incredible fast compared to the Panther version.
Dashboard is nice, fast and work well.
If you are a developer, you have olso to take a look at the new Xcode 2.0. There are also a lot of new things in cocoa that can realy help developers in speed up the building of an application (data model seems to be great). I think this OSX release will open the road to more and better write Shareware in the near future.
There are also some little security features like "Use secure virtual memory" that protect virtual memory files from other users access. Or the safari "Private Browsing" that let an user on a shared machine to navigate without filling the History.
For the one that use Quicktime Pro 6, be advised, you have to buy a new licence for QT 7.
Sorry for my bad English,
Stid.