About the Mac OS X 10.2.1 Update
This Applecare Knowledge Base article details the new features of Mac OS 10.2.1... which hasn't yet been released.
Disc Burning Enhancements
Digital Hub and Peripheral Device Enhancements
Networking and Mail Enhancements
The document provides details as to what the specific improvements are in each category.
Update: Document pulled. Mac OS X 10.2.1 update expected this week.