I've had an ICD for a couple of years, and yes there is a scar about 3 inches long, on my left chest, and the ICD sits just under the skin. It's about the size of a flip phone, and because I'm real thin, it does stick up about 1/2 inch.
I've never been shocked, but I've heard it's like being kicked by a mule. However, after it was installed and set especially for me, my EF went from 15% to above 40%, and my heart paces on it's own about 99.