First question: Iris is a Data Link Service (DLS) satellite system based on Inmarsat SwiftBroadband-Safety technology which is an update of the Classic Aero service and allows safe transfer of data from the satellite to the plane. The signal can travel through free space (no obstruction from buildings etc. ) from transmitter to receiver allowing seamlessly transfer of data. whereas this is often not the case for traditional ground based data links.
Second question: Key obstacles are that it requires that a critical mass of users are equipped with this Iris technology as well as an appropriate number of ANSPs to provide the service. In other words, it might take some time before all (European) airlines are equipped with the system, because it will require a suitable deployment plan and a regulation package including a funding scheme and incentives for airlines and ANSPs to be immediately implemented.