Way back when (December, 2009?), Dr. Klimas (and later Dr. Mikovitz) recommended not getting tested unless you were participating in research on XMRV and CFS. I know this is much easier said than done but it can happen (full disclosure - I'm waiting for my results from a large study being conducted by Drs. Bateman, Light, Light and Singh).
Until there is a standardized test, I probably wouldn't pay to get tested. Right now a positive is probably a positive but without a standardized test, who knows what to make of a negative. And even with a positive test, could you get your physician to treat you with anti-retrovirals (some might be able to but I doubt that mine would or that I'd be willing to do so outside of a study that was closely supervised by someone who knows CFS)?
FWIW