Mitochondria are pretty important (as is most of the junk in our cells for that matter). I'd be less wary of the use of mitochondria in popular science - it's shorthand for talking about the energy metabolism pathway, and doesn't indicate one way or another whether we're looking in the right spot for the causes for particular diseases / syndromes.

On a tangential note, I haven't read it, but http://www.ncbi.nlm.nih.gov/pubmed/21792218 might be an interesting review on CFS. Also, I assume you are referring to Sarah Myhill rather than her daughter.