It seems Google have made a couple of changes to the way in which it decides the position of your ad.
The first affects who can appear in the premium ‘yellow’ spots directly above the organic results. Previously, there was a minimum quality score that had to be met to be shown in these spots. If the top ad did not meet this minimum criteria (but was top due to a high bid) then it was positioned in the right margin and all other ads were put behind it on the right. This change now enables people to jump above a poor quality ad that is holding back others from the premium spots – even though it is ranked behind it on the QS * bid calculation
The second change is apparently an improvement to the way that Google factors in position when using the CTR to provide a quality score. It has always been the case that Google will provide more recognition for a high CTR that is achieved at a low position when determining the QS. It claims that this how now been improved to ensure a fairer treatment of really good ads in lower positions.
This will hopefully benefit those who have taken the effort to create a more specific structure ad and make it easier to displace those ‘high bidding big companies’ that are wasting thousands on poor pay per click!