I hate the way they market and sell it. And I hate that they refuse to submit samples for testing and certifications on some of their products. For instance, they state that their trans fluid is good for Allison, but won't submit it for TES-295 testing to use data to back up their claims. Maybe because they know it won't pass the tests? And I really hate all the reps that tell everybody that nothing else even compares to Amsoil.
That being said, I've been using their stuff in some applications for almost 20 years and have had good luck with it. For instance, their Interceptor 2-stroke oil absolutely cured the problems with the exhaust valves sticking on my F7. As long as you buy into their preferred membership program, the pricing on a lot of their stuff (not all of it) is on par with other synthetics.
Hard to really tell how good their shit is, since they only data you can find on its performance is typically what they publish themselves (obviously very biased). Again, I REALLY hate that they purposely exempt themselves from many of the certification tests.