I joined many years ago (I am a "Life" member) mostly to support the motorcycling cause politically, but I have gotten a discount or two over the years. I don't usually think about my AMA membership when buying stuff, could'nt tell you if it would make it worth your while. They do put out a pretty nice magazine which has bike and equipment articles as well as legislative news, court info, rides and riding info, etc.
Yours,
Dave
1974 CB350F