OldFaces - 2:40 am on Sep 5, 2013 (gmt 0)
Doubleclick Ad Exchange is a result of Google merging a few products. One product in particular, AdMeld, is how I got involved. Their minimum requirement was 30mm ad impressions /month.
Google is now inviting publishers of various sizes from AdSense. It is a prerequisite however that you run Google's DFP (double click for publishers) as an ad server.
Cut is the same I think. Yes, AdX will drive more revenue than adsense alone as AdX relies on real-time bidding of all adsense inventory (which is AdWords) versus hundreds of other ad networks.