For those curious about how the iPad Mini will affect your mag+ publishing, the good news is, it won't! Because the Mini is the same resolution as the iPad 1/2 (768x1024), the same MIB you produce for those iPads today will render fine on the Mini, and your current iPad app will run perfectly on it. If you're already making 768x1024 issues, you won't have to do a thing to be there and compatible from Day 1.
Some folks have asked if the same MIBs will look okay on the smaller screen. From our testing on other similar-size devices, we'd say most of them should. But we're also investigating the ability to let you upload a specific MIB just for the Mini on Publish, and will have more info about that in the next couple of weeks.