I joined the ACM in 1998, mainly to receive their journals, etc. I maintain my membership in the ACM primarily for the "acm.org" email address that I have used since 1998.
That is not to say, though, that I do not think their journals are worth reading. I simply don't have/make the time to read them. I personally think that the ACM digital library is a great thing to have access to, if your work and or leisure allows you time to read such things.
I keep thinking that someday I will have time to read all of these ACM publications I have accumulated. By then, the topics covered will surely no longer be state-of-the-art, and I will feel like I'm reading a 1983 issue of Byte Magazine with advertisements for $3000 5MB hard drives and what-not. But hey.