There has been a shortage of useful information for search marketers related to the Bing/Yahoo advertising migration - that fortunately is starting to change as agencies and advertisers dig in to the modified platform. Search marketing agency Performics has been tracking and evaluating the Bing/Yahoo paid search migration and has published some interested takeaways from its own data for the first week. On October 15th and 16th, approximately 60% of click traffic was running on Microsoft AdCenter (up from approximately 30% prior to the migration start). Other highlights include: 

Impression Volume: A lower amount of impression volume is running through AdCenter (approximately 40%), suggesting that Bing is maintaining relatively higher click through rates when compared to Yahoo!, or that a stronger mix of brand terms have migrated first.

Cost per Click: Aggregate CPCs increased during the first few days of the migration, but they've come back down to normal seasonal expectations over the last few days.

Conversion Rates: Performics has conversion rates dip over the last couple of days, but this could also be an impact of seasonality/day of week. 

Performic suggests setting up variance reports by campaign and for top keywords evaluating changes day over day, week over week and by day of week when managing during the transition.  Performics does this through its Campaigns on Demand (CoD) Automated Goal Manager, which enables rules and alerts across programs with hundreds of thousands of keywords.