small changes under the hood, nothing worth mentioning IMO
examples:
you will get a small start button but it does nothing other than take you back to metro it's not a real start menu that you're used to
added the ability to boot directly to the desktop rather than go to Metro
those are the only 2 noticeable changes IMO
others are under the hood
beware if you upgrade, an incompatible old driver might render your system not bootable even
create a system image using Macrium Reflect before you upgrade