Great asset! Gives much better control over animations in Unity. You can track when animation is finished, swap animation variants on a fly, create transitions in play mode, etc. I found it particularly useful with 2D animations, where each frame matters, and you need to change animations on demand. Mecanim becomes more of a liability in these situations, introducing another layer of logic between the code and animations. Support is quick and efficient. I've got my problem fixed in 48 hours with an updated unitypackage.
But make no mistake, it is built for programmers. If you want to use that asset, you are definitely have to be comfortable with coding. Without that, you can not properly use all of the features. The whole concept is basically "I want to have ultimate control over animations through my scripts". If that is your case, I can't recommend Animancer enough.