The pointers in the release notes are basically all that's necessary. I already found out that pages with old style layouts and new ones happily coexist. I'm really happy that the dreadful open page options are no longer necessary and that a page will be opened correctly based on the selected layout, if you update your layouts to set a layout type of course.
The biggest thing is transferring any custom CSS classes and selectors to the new SCSS / SASS / compass way. I started learning and experimenting just today. The syntax is easy enough to learn. Knowing where to put the custom stuff is way more important.