What is everyones experience with it? How do you use it?

It's a muscle relaxer. I cant take it on an empty stomach or it makes me feel ill. I use it when my neck/ back issues start acting up and it seems to help along with a heating pad. I believe mine are 500mg, they might be 750. 

For horses, I will give it to them for muscle soreness if they are tight, but rarely. I know some people give it before/ after the chiro but I do not. 

Do you get this from a doctor?

Yes it is prescription.

For horses or people?

For horses.

I had a horse on it. I didn't notice any difference. I think you also have to treat the root cause of why they're sore.