I have had a very good experience with going paleo (well mostly paleo) so far.  My energy levels are great.  My body composition has changed dramatically and I have lost a fair amount of weight.  Even my training has improved significantly.  I have had little or no problem giving up most of the paleo unapproved foods.  I do however have one thing that I have not been able to live without so far. Beer. Beer is one of my favorite things in the world!  Even though there are some good gluten free beer options out there I have not been able to give up the real thing.

What's the one no-no food or beverage that you refuse to give up?

Coffee and dark chocolate.  That's two non-negotiable items for me.

Caffeine and chocolate 

Why would I refuse to give up eating stuff that isn't food?

It's early days for me, but I'm finding myself really enjoying and looking forward to coffee.  I think I'm mostly excited because I don't get gut pain from it anymore, whereas I found it very hard on my digestive system in all my years of vegetarian, vegan and 'standard' diets.

I'm 4 years into raw paleo and I can't think of anything non paleo I still take.

Organic coffee just shoots down my liver and gives me hypoglycemia immediately.

Sweet potatoes, gum, and Diet soda.  Although I am trying to quit the Diet soda with the help of carbinated water!

Coffee w/milk
Diet Orange Crush
Strawberry Ice Cream

Those are going to be the most difficult to give up.