As for what's new. Gizmodo has a pretty good write up about it here.
[Update:] I have been installing it on a few machines already and I must say, including the download time, it takes longer than a clean install. Which I guess is probably typical since it does have to synchronize the existing windows settings, etc.. the key to any windows project is Patience!
[After the install]: Microsoft never stops amazing me with their sneaky technique in getting everyone to sign up for an account. When you went to install Windows 8 initially after the install was completed it would prompt you to sign in to your account and if you didn't have one then you could sign up. You had to look real hard for an alternative way to sign in and that was choosing the 'sign in to local account'.
Now, the process is even worse because that "local account" option is gone. What they have done is basically give you the option to sign in to the Microsoft account or choose the option that says "You don't have one" and as I have now learned, this is the way to get in without signing in or creating a Microsoft account. By clicking "I don't have one" it then goes through the process of creating one. You simply then click BACK once you are there and you are golden! Note however, you will still require your Microsoft Account in order to use the store so odds are you already have one if you are upgrading to Windows 8.1.
