Just to clarify, there are no member only events in the ABS that I'm aware of.
All our Hammer-ins are open to the public, as are all the classes. I took my first ABS class when I wasn't a member, and the quality of it, the enthusiasm of the instructor, and the pride with which the dedicated members have toward the mission statement, the organization, and each other, made me decide to join at that point.
I'm not a joiner, and I tend to be skeptical of organizations in general. The ABS is the only group I'm a member of, and I'm extremely proud to count myself apart of it.
I recommend going to the ABS website and reading the mission statement. If it's not something that resonates with you, something you feel intrinsically attached to. I don't recommend joining. If you're just looking for a leg up or a head start on knifemaking as a business, I don't recommend joining. If however, you feel idealistically drawn to the purpose of this non-profit organization of peers, if the forged blade feels fundamental to you and the pursuit of excellence, and the proliferation of that fundamental craft drives you, then, you need to be a part of the only organization dedicated to such.
Edit: Just want to clarify, that these are just my opinions, something I feel passionate about, but I'm not trying to speak for the organization or other members of the ABS. Since the OP was obviously asking for input, I'm giving it from my perspective.