Umm, when I registered my Powerbook, I got an email about the Macworld subscription. The email gave me the option of choosing an eletronic format (that works with the Zinio reader) or the regular newstand paper edition. I choose the regular magazine and I've received 3 (!) since I registered in April.
I think I completed my registration on April 1st or so, I got the email a few days later, and the first magazine showed up in about 2 weeks after that.