We've known for a long time that potato consumption is ancient. The things that actually matter, and that the paleo-sphere actually talks about, are things like how harmful the glycoalkoids in the skin are.
Here's an article discussing the actual Paleo opinion on potatoes: http://www.marksdailyapple.com/potatoes-healthy/#axzz3ikd0kh... . In short: they're okay for some people, but avoid the skins.
Obviously people's definition and how they follow the diet varies, but I think first and foremost paleo is about avoiding processed foods, sugar, certain newer foods like grains and dairy, moderating high-starch foods (which have less nutrients), and mostly eating vegetables, meats and fat.
I lost 40 pounds on Paleo/Primal sticking to 50-80g carbs/day.
That would include a good amount of meat and a good amount of harvested vegetables and fruits and no processed grains. There should be plenty of carbohydrates, fat and protein in a diet like that.
OFC when you eat 1000 cal meals you are going to have a huge sugar drop doesn't matter if it's a huge steak or whole cake. People also waste too much time on controlling caloric intake over way too short periods if you can't control you weekday intake to the required levels just lay down on it during the weekend and you'll still be fine.
All these diet's are really a waste of time and money, eat on a regular schedule (never eat when you are starving, as in never get to the point of feeling real hunger), have a diverse diet, try to expand your meals to as many a day as possible, heck I've seen people losing pounds in a heart beat by doing things as simple as droping 1 item from their lunch or moving it to an afternoon snack...
Not to mention that people don't tend to eat the leanest cut available so all of those T-Bones and Rib-Eye's add a huge chunk of saturated fat into the mix and that's without all the addons like that nice sour cream and peppercorn sauce with those nice roasted potatos....
Consuming large portions of meat will increase your BG level's they won't spike as fast as if you would chuck down a bowl of ice cream but they'll rise quite well and crash just as quickly later...