I've just installed Photoshop CC and the jury is still out on this new "rental" agreement with Adobe as far as my opinion is concerned.
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However, here is a way to see the the changes from CS 6 vs. CC for now.
Go to "Windows" and select "Workspace".
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What happens is that Photoshop will highlight in blue any areas that have a change or have been added. You can quickly go from any dropdown menu and easily see if something has changed.
While there are no instructions on what has changed you can get into these areas and play around to see what is different.
For more detailed information about the changes you'll want to go directly to Adobe's site to see what all has changed.
http://blogs.adobe.com/photoshopdotcom/2013/06/getting-to-know-new-features-in-photoshop-cc.html
Later, after checking the new features out you'll probably want to turn this off by going back into Windows, Workspace and selecting "Essentials (Default).