I agree with a few others. I have heard mine hiss a little bit, but no whistle. More like the sound of a soft breeze. I have only shot a couple of animals with them and they certainly do the job. I believe one of the blades had a curve in it after one of the kills. It was a pass through and may have hit something in the ground. I would check them real good before I re-used one. I also destroyed one trying to pull it out of a log, but that is to be expected.
I use the screw in 125 grain snuffers and the last package I bought I had a few that didn't spin right. They wobbled right out the package. I think the head is glued on to an aluminum screw-in adapter, so they probably weren't glued right. I didn't notice that on the first package I bought but I can't remember if I checked them all. They are fairly inexpensive compared to other heads, so I'll probably stick with them for a while.
As for the tips, I file them into a very small pyramid shaped point before I use them. I don't know if it is necessary but it eliminates any worry about the tip curling.