Well interestingly enough, it seems that the cellular versions of the new iPads will be sold with an Apple branded SIM card. What does this mean? Well this means that it is that you could technically sign up with a bunch of different carriers and swap between carriers depending on your needs via a menu in the Settings screen.
For example if you’re a heavy user and you’re running out of data on one carrier, you can swap to another carrier so that you won’t hit your cap. It could also be that one carrier has better reception in a particular area, so you can easily swap to that carrier instead, or if a network is down, you will have the freedom to choose an alternative.
Of course this means you’ll have to pay more to maintain your multiple subscriptions, but if you can justify this, this will save you a lot of time from having to manually swap out SIM cards. This feature is only available in the US and UK, with US carriers such as AT&T, T-Mobile, and Sprint offering support, and in the UK EE will be the carrier of choice.