I’ve known about Design Issues, but I have to admit that my interest wasn’t strong enough to buy a copy. I don’t think I have ever seen a copy on the newsstand.
My design education has been primarily through self-discovery, so I avoided the cerebral study of my vocation that most university students have to endure. I can think of only two designers I know who study design at this level regularly: Doug Powell and Michael Johnson. And I’m sure they already have a subscription to Design Issues, and/or they are downloading every PDF at this moment.