From both an author's and reader's perspective, yes, they turn out quite well. When I have color pictures, I note that in the description. I review all the pictures in the Kindle previewer for both black-and-white and color versions. If they look good on both, I also indicate that in the description. If a couple don't render well in black-and-white, I'll mention that, too (in cases where I'm not able to change the picture).