With the v201309 AdWords API release, ad group level bid adjustments are now out of Beta and available to all users. This means all API users can make adjustments to their bids when using Remarketing Lists for Search Ads criteria. You can also set bid adjustments for Display Network targets through the bidModifier field in BiddableAdGroupCriterion.

You can adjust your bids anywhere from 10% to 1000% of your original bid to more efficiently manage your bid, ad position, and ROI for different audience segments in either search or display.

Feel free to reach out to us via the G+ page or the forum if you have any questions regarding this feature.