I did it a year ago and lost well. You DO have to stick to the foods required and you MUST stay at 500 calories or you will gain. My understanding is that it's hard to get now. HHCG (homeopathic) is not real HCG and the real stuff is hard to find. It's a tough diet to stick to but works when you do.
I lost 40 lbs on it, then gained 60 in 6 months when I got off it, even though I was being somewhat careful.
I am however, considering using my Last vial right before WLS to give me a last minute edge.