Stepwise provides a small description of what's included in the OS X 10.0.1... Of note, however, they provide this tidbit: You can intercept the download, so you'll have a copy of the pkg for looking at. When the actual install is in progress, open Terminal.app and look in the /tmp directory. There will be a numbered directory (your user number in the great Unix scheme of things). Looking in that directory you should find a package called 10.0.1.pkg. This is the package that contains the majority of updates to 10.0. Useful if you'd like your own copy of the updater.