I've been using AM since 2002 but I wasn't using it a lot because I work in so many other programs. Recently I have worked in it vigorously. I’m finding out that the key to learning AM is to concentrate on making individual pieces of an object and learning to use the lathe and extrusion tool. Just get in and start using the program. Stepping through the books tutorial is very helpful. AM is a very good program compared to some of the more expensive ones like Maya. You just need to figure out how you want to create your objects. 3D modeling is reminds me of putting together a model car or plane, the only difference is, is that your creating the components and putting them together. Good luck.