I've been paleo / primal for almost a year and a half.
Never had any weight issues or any other chronic illness (that I was aware of), except I always had low energy and sometimes experienced crashes after meals. (Thought this was normal).
2 years ago these crashes became very bad (up to two hours long), I remembered reading something about crashes being related to insulin in a book by Nassim Taleb, I did a search and found out about Art Devany.
Went Paleo cold turkey, ditched all grains, potatoes as well. Energy levels were fixed, never feel lethargic (unless I've been staying up late). I fixed a problem I didn't realise I had, I just thought I was a low-energy person.
But it was hard for me to keep on any weight (I'm skinny and want to gain weight) so I added potatoes back into my diet and eat them almost every day now.
EDIT: Just to add when I do manage to gain weight I don't notice any belly fat or anything, which was starting to happen for the first time before I went on paleo (and so must be the result of grains?)
My energy levels are still stable, no crashes, don't feel lethargic.
So it seems that wheat was the real issue (bread, pasta etc.)
Stephan Guyenet, Richard Nikoley and Mark Sisson seem to think they're alright, last I heard.
Do you eat them? Do they effect your energy levels or weight?
Are wheat products much more hazardous for your insulin regulation that potatoes even though they are supposedly high glycemic?
EDIT: Found this thread which comforts me in sticking with tubers http://paleohacks.com/questions/15961/potatoes-unfairly-maligned-in-paleoland#axzz1YEXlSuX7