Here's the latest post on the topic on the Adwords blog [adwords.blogspot.com]
Last month, we posted about upcoming Quality Score improvements -- and today, we're following up to notify you that these changes will take effect in all advertisers' accounts over the next few days.
They're calling them improvements, and in the previous post in August [adwords.blogspot.com] being referred to, they're explaining some about how query time quality evaluation works.
Most importantly, we are replacing our static per-keyword Quality Scores with a system that will evaluate an ad's quality each time it matches a search query. This way, AdWords will use the most accurate, specific, and up-to-date performance information when determining whether an ad should be displayed. Your ads will be more likely to show when they're relevant and less likely to show when they're not. This means that Google users are apt to see better ads while you, as an advertiser, should receive leads which are more highly qualified.
How can there be a rating given for an ad if it's now done real-time and it's query dependent?