I'm staying for a while in China (Beijing), and signed up for Ofo. Unfortunately, I didn't know that they have quite a bad reputation. About 1/3 of the bikes are broken, and nobody bothers to collect or repair them.
More worrisome is that they seem to have an unsustainable business model. At signup you pay 99 RMB (for Mobike it is 299 I think), and they you should pay per ride - but I've only once had to pay at all, most of the time it is 0 RMB. I guess that's also why they don't care that much what happens with their bikes. Their only income is new sign-ups.
By the way, the latest Ofos also have digital locks, and even Bluetooth. And there is a new generation of MoBikes I think which is a lot lighter. It is interesting what kind of new technologies MoBike uses, like airless wheels, where the tires look like swiss cheese from the side to save weight and roll lighter. Or a chainless drive.
About the stealing, I have the opposite experience. I think Ofo has proven that you can just slap a combination lock on a bike, and honesty or laziness will keep people from stealing them. I mean, where would you store the stolen bike? In front of your house, where there are hundreds of other Ofo bikes that cost next to nothing?