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We used IGA for our game. My personal experience - not speaking on behalf of our company - was that it was a bit fiddly to use. The API, despite being really small, seemed to change quite often, and they could be quite demanding about how much effort you had to go to in order to register an ad impression (to the point where performance could potentially suffer).

My experience is a year or more old however and I can't comment on the current state of their offering.