I use them and have been using them for about 7 years now. It works very well, but as always there are exceptions to the rule. If a cow has very long teats I have seen calves still suckle the very tips of the teats, how much milk the calf was still getting this way is anyone's guess. Other calves get very crafty and turn their head on the side and still suckle without the spikes touching the cow. In the 7 years I've used them there was about a handfull of calves that it didn't work on.
They can be re-used, but not indefinately, I have had some break where the bolt head is on the inside meaning you can't tighten it anymore with the wingnut. Also once they get old and hard from the African sun some will break when you take them out, but that is minimal. Some wingnuts also rust to the bolt if left in too long.
About the only other negative is that often the ball of nosering grows through the septum leaving both balls in the same nostril, then it takes some practice getting it out. If its a bull that will get a nosering the hole is there already so it can come in handy as well.
I have used both the type in the picture and the metal one with the floppy plate, the metal ones can get very hot in the sun and I imagine very cold in your climate and calves find it easier to manipulate them than the plastic spikey ones in the pic. Usually after a week or two of having the noserings in you can remove the calves from the cows if need be without having cows breaking every fence in the way to get back to the calves. In my situation is a very handy management tool.