I think they are good for the average hands, especially shooting duelist. They are second only to the Bisley in this respect. I have a pair of Ruger Birdsheads in .45 and they are great. As noted they do roll in recoil but I don't find them to roll too much.
As also stated, try to shoot them before you buy them as you will either love them or hate them.
I love them, but I find that Bisley is better for duelist. it's about the hammer, not the grip shape for me. If I had slightly longer thumbs I could be quite happy with the Birdshead over the Bisley.
I also shot the Birdsheads traditional style and they work well for that too.