"As previously noted, the 10.1.1 update delivers improvements for many USB and FireWire devices, including support for additional digital cameras, and overall improvements to CD burning. Enhancements have also been made to AFP, SMB, and WebDAV networking, as well as improved printing support. Mail and the Finder have been tweaked, and hardware-accelerated video mirroring has been enabled for the new PowerBook G4." /ThinkSecret
A friend of mine installed but didn't notice much of a difference in regards to overall system speed. But then again, that wasn't addressed either.