In an Inside AdWords post we are told
As part of our ongoing efforts to help improve the quality of our ads, we’re announcing an update that changes how each keyword’s 1-10 numeric Quality Score is reported in AdWords. Under the hood, this reporting update will tie your 1-10 numeric Quality Score more closely to its three key sub factors — expected clickthrough rate, ad relevance, and landing page experience. We expect this update to reach all advertisers globally within the next several days.
That next several days means that most, if not all, AdWords users will see this update this week.