A few months ago, Google added impression and click data to Google Webmaster Tools. It was very cool, but today, it seems like Google quietly launched percent change and position change over time to those reports.
Here is a screen shot:
As you can see, next to each column it shows the percent or rank change over time. I assume the change data is based on the date range you selected compared to an equal previous date range.
Also, @davidburgess00 noticed the parameter handing has it's own tab now. Here is his screen shot:
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