I used to subscribe to Zymurgy way back when it first started and it was a great magazine full of important homebrewing oriented info on materials, ingredients, techniques etc. Now I find it to be mostly a fan magazine for the AHA and its competitions - especially the competitions. Sometimes it seems that the whole magazine is devoted to "how to brew beer that will win competitions" rather than making great beer(not necessarily the same thing). If you're into competing, then I guess that's fine, but I find it to be a turn off.
I do pick up BYO at the bookstore and have serioulsy considered subscribing. I like its focus on materials, ingredients, techniques, styles and brewers - like Zymurgy was in the old days.