While much of the interface is unchanged, when you dive into an application's page (or a book, or movie, or music) you'll see the big changes. New animations, new badges, an awesome header of the associated video (if one is included) are just the beginning, and the whole design of the new content pages looks to have been built from scratch with the new design language.
There are some changes to get used to, as well. Content descriptions now are displayed full screen, and this is where you'll need to look to see any change logs. This is also where you'll find information like version number, the last update time, or the number of downloads.
It looks very nice and has us pumped to see the next version where more of the design has been updated.
Via: +Kirill Grouchnikov