I was cautiously skeptical of them, having been an ER nurse, however I think they are great.
My wife used them on a trip to Austin, the Lime scooters are available for rent. She went on and on about how great they were. We were in LA and were out an about and realized renting some scooters would be really handy. I cautiously got on one and within a few minutes, felt rather comfortable on it. They were incredibly useful for short distances, like 0.5 -> 2 mile distances, quickly.
I think the biggest factor for whether these are safe as transportation methods depends a lot on the city where it will be used. Cities that have rental fleets strewn throughout them, the drivers are accustomed to seeing them and sharing the road with them much like bicycles. Cities that do not, drivers aren't as accustomed to seeing them and will not be as comfortable driving around them. Cities that have dedicated bicycle lanes (real ones, not BS ones that are essentially just lines painted on the road) will also be safer as these drivers are also more accustomed to sharing the road with other modes of transportation.
My town does not have rental fleets, but I see people on them somewhat regularly commuting, so drivers are being exposed to them. I would absolutely consider one of these if I needed to get a couple miles from my train stop.