Looking at the update file itself, it went from 3.0 (515460094) to 3.0.1 (525120101)
The kernel was updated along with the kernel modules. Somebody mentioned that the 5 way repeat is different now.
169 file patches. Most of them are very small and don't appear to be changing very much. The files with significant changes are the browser, the reader, Topaz support, font support, character sets, some sort of API framework (KDK?) and the home screen.
I haven't gotten around to examining the changes to the Kindle source release yet.