I don't subscribe to many magazines anymore. But I do subscribe to two auto and two motorycle magazines. What keeps me coming back when I can get all of the latest news and reviews for free online? High quality writing. For the most part, just ain't the same on the Web. Certainly in the car and bike field. As long as guys like Jamie Kitman, Ezra Dyer, John Phillips and (the semi-retired) Peter Egan keep writing, I'll keep buying. But I also second Luke's remarks about needing to do a good amount of my reading away from a screen.
I wonder which magazine that is? I also get a few motorcycle magazines and I like the stories and most of the travelogues. Like you say, really good writing makes a magazine worth while.