Fine for me...
I use a D4 as one of my EDCs and it's seen a lot of use. The cutouts are as close to perfect for my hand as I could imagine. I use two fingers in the first one, one in the second, and my little finger in the last one, your basic sabre grip. It's a fine combination of secure grip and cutting control for me. I'm probably average size (5'11") and I do mostly pull and push cutting chores (bags, boxes, plants, etc.)... no real detailed work.
I have, however, occasionally used my D4 with my first finger forward of the handle on the square part of the blade and my thumb on the ramp. I don't recommend this, but that has allowed a little more control for some tricky cutting.
I think it's a great handle for that sized knife.
"If there are no dogs in Heaven, then when I die I want to go where they went."
~ Will Rogers, 1879-1935