A couple things I've noticed about the Stihl hatchets and axes, the palm swell is too gradual and doesn't create a 'hook' for the pinky as traditional American hickory hafts do. I also find the grip to be overly round. I'd prefer it was a little more oval shaped.
They are pretty decent choppers, especially for the lighter tasks you would perform with a hatchet. But they are a little sticky for splitting because of the slim cheeks and the abrupt transition from thin cheeks to the fat eye. The fat eye is necessary to accommodate enough European ash to match the strength of a slimmer piece of American hickory. With ash you just need more wood. This could be influencing the thickness of the grip and palm swell but I really don't think all the thickness is needed down there.
I think it would feel better in the hand if the swell were rasped out a little as I've tried to illustrate in this image.