What's in an update?
You can look at the Google Changes for each release of android, but this device uses Samsung TouchWiz. This release contains the Google changes, plus the changes that Samsung made. I do not know of a "change log" page that Samsung has.

I read that this version is the official Gingerbread 2.3.5 release of Android TouchWiz. But also, if you use a USB Jig, that it breaks the that functionality.