I never done slimfast so can't comment on it. like every other diet if you put your heart and soul into it then its good. I don't buy all the vitamins that they suggest as I have been taken a multi vitamin this years and I didn't want to give up that one and try something new. The fibre I don't purchase either as I have IBS so it has actually done the bowels the world of good being on this diet.
I have a breakfast and two snacks all day and then two shakes. I done really well for the first few days and then fell down because of so much junk around me with xmas. I tend to go fully at it after xmas is over.
Good luck everyone.