Anyone have any experience with them?

Go over to longrangehunting.com. There are several threads about them. Seems like almost all are positive. The only negative is when someone tries too heavy of a bullet in a barrel without enough twist to stabilize it. Other than that those that use them are quite vocal about their effectiveness and accuracy.
Bruce

They are made of copper, and I would guess they will perform like any other bullet made in copper.

We have extensively shot them and load them for all our client rental rifles. We have been shooting them for close to 4 years now and have taken 100s of animals with them.

They are a great bullet and work very well. As someone stated as they are 100% copper they are long for weight compared to a traditional lead/copper bullet. If you go too heavy and have a slow twist the accuracy may suffer. I recommend dropping one weight, I.e for 30-06 if you shoot 180 drop to 165 grains.

As Saeed said they perform like a copper bullet and recovered bullets look very much like pics he has posted of his recovered bullets from his design. Nothing is 100%

I shoot a 30.06 18"barrel and suppressed and shoot the 150 Power Hammer at 3034 fps and found on the 4 animals I shot in SA this past April I could not ask for better performance. as for load development I have never just picked a powder loaded up and hd the gun sighted in and shooting 1/2" groups at 125 yards and then worked on the velocity, no need to look for coal just load them the length you want. great bullet

I used the 281 grain Hammer Hunter bullets in my .375 RUM for my Alaskan Brown bear hunt last year.

My first shot knocked him down, but when he got up my guide said to keep shooting until he didn't get up, so I did.

I think that most bullets completely passed through him. My second bullet was a Texas heart shot as he was running away, and when we were skinning his rear, the worms coming out of that area quickly made me decide not to dig around to recover any bullets.

He was the prettiest bear that we saw...