Thanks, I appreciate your feedback. I've used many ads in the past for none gaming apps and I remembered Admob has the lowest eCPM of them all, but their fillrate was close to 99%. Amazon initially offered a high eCPM, but after the first year, the eCPM dropped back to normal with low fillrate.
Since I'm using AppGameKit it's not like I have tons of Ad choices, so I think I will setup the Ads hierarchy based on
1) Chartboost
2) If no chartboost ads exist then display Admob
I'm not sure if Amazon is even supported for IOS or not?
BTW, Pixelstein art style looks awesome! Reminds me of Doom and I'll definitely dl the game this weekend.