Proof of Stake (PoS) is a really great model, but I think the Instant Payment System is taking its place in a way. Transactions will be handled the system at great speed, but at the cost of true blockchain-style security.
Electroneum’s headquarters will now effectively become the only master node in this case, which basically makes a decentralized technology centralized again. However, they are not truly a master node, but rather a hybrid entity, since all transactions will still need to be processed by the broader blockchain mining community in due time. The instant payment system will only act as a sort-of easy-to-use front end to blockchain’s ugly code, but what happens behind the scenes will still be secure.
And of course, people can still use ETN without ever touching Electroneum’s servers, although at the cost of transaction speed.
I agree with @Mulder that proof-of-work mining is helping the unbanked get traction in crypto. But one also needs to consider that ASICs are dominating the ETN mining space at the moment, which themselves cost a couple hundred bucks each, and kind-of eliminates the small third-world players who can’t afford ASICs.