Question about the birth control Mirena!?

Has any females gotten the mirena IUC? Did it hurt? A lot of people have been telling me they know people who have ended up pregnant and had it. Does anyone know anymore about it? I read the brochure my OBGYN gave me but I was wondering if anyone else knows anyone who ended up pregnant? The brochure says it is more effective than having your tubes tied or a vasectomy.