A few personal thoughts when testing the Visual Studio 2013 Preview.
The first thing that I noticed was the login. This helps Visual Studio syncing between machines. Is this a good feature?
Well if you are like me having several developer machines at work and home then it might be a good idea. You can change what will be synchronized by changing the settings in Tools | Options.
Second thing is the color schemes, I would argue that is a good feature making it easy to switch between an brighter theme on day time and a darker to use in the evenings. This can also be changed under Tools | Options later on.
The notification in the upper right is good, discrete but let you notice that there are updates to download etc.