(1) Improved how they normalize the formula for taking into account ad position when calculating an ad’s click-through rate. (2) Enabled more ads to reach the top ad spot, through a revised ad promotion algorithm.
If you have questions about either change, please let me know and I’ll ask Google on my call with them at 3pm (EST). To let me know about your question, either send me an @rustybrick via Twitter or contact me via the form. Please submit only related questions to this specific update and please submit your questions early.
So far, I have not seen any complaints in any of the search forums I track, in regards to this new change.
Postscript: The answers are live, and well worth a read.