I guess it depends on the baby (how much speed they gain) and supervision. Just like any baby toy there should be adult supervision, there's horror stories about everything in this world and you need to take everything you hear with a grain of salt.

Personally I haven't got one yet but if we were given one id give it a go, my mum said us 3 kids all had walkers with no accidents, she said it was great for my brother cause he has Down Syndrome and could hold himself up but couldn't walk til 2 or 3 yrs old and it allowed him to walk around and actually build his leg muscles (he had hypotonia which is poor muscle tone at birth).