I'm very much interested and excited about this, based on what has been shown and backed up by the comments by Phil Spencer. As has been mentioned, at least visually (all we know at this point) it blows the socks off every other flight sim to come before, and I'd say likely visually sets itself above anything else currently in development, flight sim wise. With the fidelity and accuracy of the world depicted, I can see this appealing to a far wider audience than those who just have an interest in aviation. Having spoken to various friends and family members over the years about flight simming, who have no real interest in aviation, they have however often expressed an interest in just knowing enough to be able to use the game to explore geography, cities, historic sites, etc. Up until now, games such as FSX, P3D and X-Plane wouldn't hold the interest of individuals like those, since, at least out of the box, those sims don't have the visual accuracy, fidelity, etc. to truly convey flying over the real world and have the experience of looking down and believing what they're seeing is real (except for certain addons, and for which typically only the highest fidelity is in quite small regions, centered around airports, etc.). Based on these previews, it looks like that will be changing. If we can expect at least large regions of the world to have the same visual experience, accuracy and detail as shown in the previews, it's going to be a game changer for sure. Rather than simply using scenery as a background, or tool, as is almost solely the way that scenery has been in flight sims to-date (again, at least out of the box), if we can expect the scenery in this new sim to be what is shown in the previews, the scenery itself will be a reason to go flying, more than just the act of operating an airplane alone.
With a 5-year old system, and still running Windows 7, I supposed I shall start saving my pennies now (good to know we have a year till its release)...