The Apple SIM allows the user to select any short term plan from any carrier right in the Settings.
The new SIM option is an enormous change benefiting any regular traveler, as they are no longer beholden to one carrier. This also means that, while traveling, users can select different local carriers for a short-term data plan.
This eliminates the need for a SIM card, or that scurry around a location to find a local SIM upon arrival in a new destination. These sorts of localized carrier partnerships will be rolled out over time alongside this new tech feature, with AT&T, Sprint, T-Mobile and EE among the first US and UK carriers to support Apple SIM.