I think the most exciting part is their use of electric ion propulsion to maintain low earth orbit. If SpaceX ever goes bankrupt or something, the satellites will passively deorbit within 5 years or so.
No need for that actually. They will deorbit within a year if left completely dead, and within a couple of month if they have a single button "start deorbiting" that uses the electric propulsion.
But more importantly, their propulsion allows them to launch at a very low orbit. This is a very good method for a constellation as they can see all the early failures (the beginning of the bathtub curve) happen at a very low orbit and reduce the cost of ground testing.
Their orbital debris management strategy is one of the best I have seen.
Yup, and I think this could be improved further by using even lower orbits. Improves latency, debris, and reduces visible time (i.e. closer and closer to only visible during twilight... plus the closer distance increases apparent angular speed and thus reduces dwell time per pixel) for ground telescopes. Requires a bigger propulsive burden, but this is worth it, IMHO.
And launching to lower orbits means higher payload to orbit per launch which means they can launch more of their constellation per launch. (Although they probably a larger constellation at those orbits just due to how short the orbital periods are.)
But more importantly, their propulsion allows them to launch at a very low orbit. This is a very good method for a constellation as they can see all the early failures (the beginning of the bathtub curve) happen at a very low orbit and reduce the cost of ground testing.
Their orbital debris management strategy is one of the best I have seen.