I've heard some horror stories about semi-permanent eyebrows. Some people end up happy with the results and some people end up shocked. My friend had a semi-permanent eyebrow tattoo done and she looked like a clown at the end of it. Her eyebrows were thick, dark and a block of color like she went crazy with a black eyebrow pencil on them. They did fade over time, but she almost always avoided social events during that time frame.
I know many people do not experience such disastrous results, but if the tattoo artist is not good at what she does, eyebrow tattoos are a very risky thing to do.