Combined with the recently added top vs. side segmentation in reports, this metric gives advertisers increased ability to target their ads at the position they want and to measure the results from a top vs. a side position.
Google stresses that the estimated bid shown does not guarantee a top position for your ad. All the usual factors still apply (Quality Score, budget, account settings, competition at the moment of an auction, etc.).
To view the new metric, go to the keywords tab in your AdWords interface, click Columns, select “Customize columns,” and check “Est. top of page bid.” Save the column configuration, and the metric will now be a column in your keyword list.