While my CAC on Yahoo's system is a bit lower, I actually wouldn't mind having 1 interface to manage my two CPC campaigns as Google's system is slightly better.
I am however worried about what this means for cost, as MSN isn't even competitive in this market.
Interesting timing..first the Quality Score update and now this. Yahoo's quality/bid algorithms are completely broken- I wonder if Google's QS will now apply to all Yahoo ads.