Google is testing a new user interface for the AdWords ad preview and diagnostic tool. The new look drops off the left side bar and shows the preview in a larger view. Avinash Murthy spotted this and posted it on Twitter.
Here is the test look:

Here is the look that most people see:

Instead of showing the options and search box on the left, they are showing it at the top. I assume this is to start to make this more mobile friendly.
What do you think?
Forum discussion at Twitter.