I have them and they take a little getting used to but they are great if you have a big moving horse or a strong horse, I have one of each LOL, as they really do help you absorb the movement and the wider stirrup tread gives you more grip.
They ave helped my OH's lower leg position too, he always found it really difficult to keep his heels down and since changing to these he is much better and his ankles dont ache anymore.