I have had the bad experiences similar to others, where you just feel they are handing out the same bland stuff that everyone knows, 5 a day, more fuit and veg, less sugar - YAWN!
However, I have also seen one who was great, actually prepared to listen to my lifestyle, single person, variable hours, out most evenings (mix of exercise and youth work, before you accuse me of pubbing!) and so needing to be home and out within about 45mins.
She then actually gave it some thought and gave me some very useful hints and tips. I especially liked the one about eating more meat(protein) and less potato (carbs). All I need to do now is fit in the fruit and veg too.
Best advice, as previously said, be ready to stand your ground and say 'er no, that wouldnt work for me because....'
But apart from that remember they are there to help not judge and have little clinical input into things anyway.
Cheers
Malc