Great for Indie game developers/studios
I've been working with them and using their MAS service for nearly 2 years, and it's been a great experience. I switched from Admob and got a 2-3x increase in ad revenue almost immediately. Support has also been nothing but great. What distinguishes these guys from the rest is that they genuinely care about your growth, not just for the game, but for you as a studio. They actually play your game, give meaningful feedback on areas to improve and provide technical help. In all honesty, they take about a 10% cut if I'm not mistaken, but it's extremely worth it considering your revenue will most likely receive an increase well over that percentage when switching. Not to mention of course the support you'll receive on top of that.