Google announced that the quality score metrics are more real time based on a per-query level, now. Not that this has been implemented on everyone's campaigns yet, but it will happen soon enough. Since then, advertisers have been noticing anomalies with the quality score being reported by Google.
For example, a minimum bid of $0.05 typically had a "Great" quality score in AdWords. But now people are seeing a quality score as marked as "OK." Here is a picture:
When I click through to see more details on why this keyword only has an "OK," I notice there is nothing I can do better here:
Keyword Relevance: No problems found. Landing Page: No problems found. Landing Page Load Time: No problems found. (Load time is faster than the average in your server's geographic region.)
Several advertisers have also noticed this and are discussing it at WebmasterWorld. They think it may be a bug related to the new quality score metrics that are coming out way.
Forum discussion at WebmasterWorld.