I used PN for a couple years and found it to simply be too much work. Too many meals per day, lots of nutrient timing that I don't worry about any more. Using protein shakes as meal replacements, smoothies, etc. I know it works great for some people, but the way I was going about it didn't work for me. I'm much happier eating my 2 or 3 meals a day, when I'm hungry, and just eating the primal foods I choose to eat. I was hungry a lot doing a non-Primal version of PN, and some of the protein shakes left me still feeling hungry. To me, Primal/Paleo feels a lot more "natural" and non-intrusive.