So I bought one. See my video review, and read additional notes below, to see why they won't change the world, supplement bikes, trains, buses, and metros, and save cities, historic neighborhoods, and our resources. For some shockingly obvious reasons, they might kill you.
One thing I don't mention in the video (there is only so much time before you would fall asleep from boredom), is that the scooters are only good for transporting one human body and nothing else. The manufacturers instruct not to carry anything on the handlebars, or on the deck at your feet (as if there is room); the resulting imbalance could be dangerous in many situations. I would add draping a messenger bag or backpack across your body. The inherent instability of the scooters could be dangerously exacerbated by shifting loads.
Yet another caution: posture on the scooter leaves you vulnerable. The natural instinct and manufacturer's manual has you with your feet at a diagonal on the deck. Your torso has to twist to face forward so your hands can grasp the handlebars. Your head is also rotated 45 degrees to look forward.
Without a rearview mirror, it is inherently difficult and dangerous to monitor traffic behind you without losing balance, or reacting to changing conditions in front of you. It only takes a fraction of a second of distraction to endanger yourself or others.
So, you are left with a device of limited utility. Think about how often you go to and fro without so much as carrying a muffin, book, a purse, or a purchase. That's about how often you could, and should, use a scooter in daily life.