I like them & used them.
My children were only in them around once a day, sometimes every day, sometimes not. I used them more to get the kids up off the ground when they were getting frusterated with not being able to do it themselves.
By the time the worked out how to walk in them, they weren't interested in them anymore as they were crawling, or cruising & didn't like being restrained.
They aren't great near stairs...for obvious reasons. I've never been silly enough to use one near a step. Although they are made to lock up so they can't go any further if one wheel goes over a step.
My last one was made that way, it was impossible for me to even push it over the step into another room with my foot while holding DS. I still refuse to trust them near stairs though.
Balconies aren't the best idea either. My children weren't in them long enough to get up any sort of speed, but I did hear of a friend who hit the balcony rail in a walker & it gave way. Lucky it was only small.
They aren't the best or safest things, but, if used right, I don't think they are damaging either.