Transparency – Later this week, we're releasing an optional Quality Score column that shows the minimum bid for all of the keywords within an ad group as well as a Great, OK, or Poor quality label for your keyword.

Quality – Next week, we're launching improvements to the Quality Score algorithm that sets minimum bids for keywords in order to improve the quality of ads that we serve to our users.

http://adwords.blogspot.com/2007/02/quality-score-updates.html