Does IBooks sell magazines. Being in Canada we can't even get latest releases yet. I know about Zinio however the app is not as good as IBooks. I don't want to subscribe through Zinio only to find out they will come out through IBooks.
To quote The Cars, "It's all mixed up."
Some magazines, like GQ and Wired, have created their own apps themselves. Some publishers are apparently using services that digitize the magazines for them, like Zinio and Pixel-mags. Zinio seems to handle everything for you, digitizing, downloads, subscriptions. Pixel-mags seem to create digital versions of a magazine and leave it to the publisher to handle distribution and collection.
As the market grows, more and more publishers will decide how they want to enter it - simple apps that let you read the magazine, full-on bells and whistles versions like Wired, or somewhere in between. My guess is that it will depend on their audience and how much digital content they're already producing.