I just downloaded and installed Visual Studio 2013 Preview. Here is a list of some changes I noticed right away.
When you start Visual Studio first time, it will ask you to create a Visual Studio profile or use your existing Microsoft profile. So now Visual Studio connects live with your account and settings and data can be saved online that you may access from any devices from anywhere.
Once profile is saved, Visual Studio 2013 has three different themes to choose from - Blue, Dark and Light. I like Blue theme better than other two.
The Start Page looks like the following.
I will be adding more updates as I go.
Feel free to let us know what other features you see and like.