With the most recent version of my game using Appodeal, I have watched the fill rate drop significantly, which means revenue has also dropped significantly. My users have reported that ads are not showing at all much of the time, and when they do show, they are almost always Unity ads, which don't seem to produce much.
Needless to say, I am less than impressed with Appodeal, but I am also not impressed with the dismal amount of revenue that ads produce in the first place. The Amazon Underground model makes much more sense to me when it comes to giving my hard work and intellectual property away for free.
By the way, @simwhi, my adMob account was suspended for some reason as well. They wouldn't tell me why, but still expected me to "fix" it. Appodeal is still working, but that's probably why my fill rate has dropped and I'm only getting Unity ads.