I was asking myself the same thing ...
I think our uncertainty and confusion are shared by the magazine industry itself.
Everybody seems to sense the potential here. But nobody seems to have figured out what to do with it. Even companies like Condé Nast, which seems prepared to go all-in, have been hazy about the details.
For that matter, even the New York Times, which had reps up there on stage at the product announcement, is reportedly still anguishing in-house about how much to charge for access -- and they may be farther down the road than anybody else in the publishing business.
So, educated guess time.
Big magazines, and smaller tech-savvy magazines, will probably develop custom iPad apps.
Subscribers (paid and otherwise) will be able to download most content automatically whenever an update is available and read it offline.
Most but not all: I suspect that large video files and the like will require a live internet connection. If you're online when you click to view the video, you'll see it right away. Otherwise you'll get some kind of prompt to go online to view this content.
So it's a mixed picture. A publication like The New Yorker, which is mostly text and pictures, will be totally downloadable and viewable offline. Something like Sports Illustrated, which may have lots of game highlight videos and other cool things, will require you to be online.
But really, at this point, nobody knows -- and perhaps more to the point, the people at The New Yorker don't know what Harper's is going to do, and Sports Illustrated doesn't know what ESPN is up to. This is an industry (trust me -- I just did my taxes, and a plurality of my income last year came from freelance magazine writing) where the ONE THING every editor cares about is what every other damn editor is planning for the next issue.
These are pretty smart and hip and design-conscious people. But they work for organizations that have stripped themselves down to bare fighting weight over the past few years, mostly because competition from new media has cut drastically into ad revenue and, often, circulation. So now you've got the weird situation where there are exciting new possibilities to think about, but no one on staff being paid to think about them.
