I have used the Apexi AFC, Apexi Super AFC and Apexi Super AFC II... They aren't worth it. You already mentioned how horrid his tuning was, that is because the Apexi AFC is fairly inadequite. If you want something that operates in the same fasion but is 10x better, look at the Greddy E-Manage Ultimate...

(note, I have not used the Apexi Super AFC Neo, but it's just a newer Super AFC II and wouldn't be worth it in my opinion either, even though I don't have direct experience with them).