there are some scooters you can buy that go way too fast, but the ones you can rent usually max out around 15mph, and that's only on a warm day with a full charge. it's definitely less stable than a bike, but every time I've hit a pothole I've just ended up awkwardly running alongside the scooter for a few steps. I'm not quite sure what people are doing that leads them to eat concrete. I've certainly never seen it happen in my city, even with squads of drunk college students riding them on the weekends.