The Google AdWords Blog announced that they are changing the top ad placement algorithm, i.e. the promotion algorithm, a bit. I was actually briefed by Google's Nick Fox on this change and posted a lot of details over at my Want That Top Ad Position On Google? The Rules Are About To Change at Search Engine Land.
In short: Instead of using the actual CPC, it will use the ad’s maximum CPC.
That is the main change in how Google will determine which ads to place in the top positions, directly above the organic results.
Google has written up a detailed FAQ on this top ad position. It will go into affect within a few weeks, and I will be tracking the forums to see what type of impact this will make on the advertisers.
Forum discussion at Search Engine Watch Forums.