Unfortunately, that enthusiasm is turning into frustration.
All Things Digital is reporting on Time's trouble with getting a mutually-agreed upon subscription model past Apple. Writing for All things D, Peter Kafka notes that Time wanted to launch a subscription-based version of SI on the App Store, only to have it rejected by Apple.
Time would have users download the app from the store and then pay them directly for future issues. Apple didn't like the idea, and Time was forced to sell single copies of the magazine. Right now when you launch the app, you're presented with a number of issues that can be bought, in-app, one at a time. All of the magazines I've read on my iPad, like WIRED, Outside and Popular Science, use in-app purchases.
We'll see what happens as this new union of publisher and distributor grows.