We have some at the shop with R-8 shanks. Worked great on 6061, acetels, 660 bronze. They didn't seem worth a damn on steels. The problem is that the radius on the insert increases the cutting forces over square cutting insert mills. As long as tou restrict them to light surface cuts you should be alright. One nice thing is that you lunch the insert completely you should be able to get 16 edges out of them. We got them through Valenite so we probably paid a stiff mark up. First saw these in a toolsupply house in Racine WI about 28 yrs ago. so they've been around while.
The optimist says the glass is half full, the pessimist says it's half empty. The paranoid in me says somebody put a hole in it.
Remember pessimists are at heart opptomists. They know things can and will get worse.