OldFaces - 4:01 pm on Sep 5, 2013 (gmt 0)
That makes sense re: the qualification levels. Again, I joined AdX slightly before Google began pushing more publishers into the network. I think as long as one has DFP running and generates decent revenue they will eventually get invited.
Re: your concerns, IMHO I agree they are valid. However, the minimal additional insight Google receives about your website (that they don't receive already with adsense & analytics -if you have it running- & chrome) shouldn't sound alarm bells.
I will tell you that you will see a significant lift when you begin running AdX over Adsense. However, to benefit to the full potential there are optimizations that are needed. I will try to post more later with details.