Windows 8 startup is faster. It beats Windows 7 in most benchmark tests, but not by enough to make it very noticeable doing every day work. No hardware or driver issues for me.
File History is built in now, so old versions of files can be restored. Back in my tech support/help desk days people constantly wanted to recover old versions of their files.
Skydrive integration similar to iCloud has been added.
Drive Extender from Windows Home Server was added allowing multiple different size drives to work as one in Windows.
For people with kids... Parental controls have been improved with time limits, site/app blocking, website history, search term history, store download history, most used apps, most visited sites, etc.
File copy progress windows now automatically stack in a single window if there is more than one...
This menu pops up now when you right click where the start menu used to be...