Amsoil makes great products, I don't think anyone can deny that. The problem is that there are plenty of other products that work just as well, cost considerably less, and are far more readily available. I'd be much more likely to use Amsoil if I could just go to the store and buy it at a price that was competitive with M1 or other name brands.
The other issue is that Amsoil doesn't carry any manufacturer approvals. With the increased cost over other brands, it should at least carry manufacturer approvals and not just say it's "recommended" for a particular application.