I have not used them so take this for what it's worth.
One of the bow companies I do business with does not recommend them. They are too light and hard on the bow.
My personal feelings?
They are too light for hunting.
For the best results I feel you need a combination of speed and weight for good penetration.
I would also think that this light of an arrow would have to make the shot louder?
Until we reach speeds of OVER 1100 FPS, the animal will still hear noise before the arrow hits it's mark.
I have some "hot rod" Maxima 250s (341 gr) made up and they are significantly louder thru every bow I have shot them out of than my Maxima Hunter 350's (410 gr) that I will be taking to the woods. I have even used the 350s for 3D just because I want a nice, quiet shot.
I did the KE formula on both arrows and while the light 250s are only 1 lb less than the 350s I feel the 350s will do a MUCH better job of passing thru deer.
I know, I know, bragging about how fast your bow is, is fun. But, having a full freezer is better :sad: