I like these: they fit nicely on running shoes. Running in snowy/icy condition is easier. However, there are cons. Like all Yaktrax, snow tends to accumulate at the eel (noticeably so). Another issue is the cleats, if you are a road runner, the cleats can be an issue when surface changes. I live in an area of rapid snow and thaws, so patches of dry ground occurs frequently: the cleats make it jarring when hitting dry ground. It's unpractical to remove the traction device every time the ground is free of snow/ice.
So in the end, this is  a good device when the ground is entirely covered in snow and ice, not so much if it isn't. I am sure that it would be good for dirt trails (granted that there are no large rocks, such as you would find in old river bed or mountainous area). I am glad to have them but it's not a must to have. Good running shoes will work just as well without any of the cons.