Though the authors of the WPI cytokine study (see Immune Abnormalities in CFS — Two New Studies) infer that this confirms XMRV in CFS, I do not believe this is the case. It simply shows that in a CFS patient whose illness began with an acute viral infection, you will see a characteristic pattern in their immune lab tests.
What I think the new WPI study does very well is to offer a promising new test for people whose CFS began with an infection. For those who are working with family members or insurance companies that still don't believe their illness is real, this testing may be very worthwhile when it becomes available.
On the other hand, I would note that I also recommend that the "Expression of Concern" by the editors of the journal Science, which raises the question of XMRV in the initial WPI study being a contaminant, be viewed as simply that — a question or concern. This concern is based on two more negative XMRV studies. News reports that this means the WPI authors should retract their XMRV study are very sensationalistic. I personally consider calls for the study to be retracted to be absurd, for the reasons the WPI authors note in their response.
To put it in perspective, as cholesterol medications have been shown to not really be helpful in primary prevention, antidepressants have been shown to be about as effective as placebo for mild to moderate depression, and many diabetes medications actually are more likely to kill the patient than help them (and the list goes on and on and on), does this mean the journals will soon be requesting retractions and attaching "letters of concern" to thousands of these earlier studies? Unless this becomes their new policy, it is equally ridiculous for them to be doing so here.
I suspect that the XMRV debate has yet to be resolved — and I have discussed repeatedly what is needed to resolve it, which is fairly simple to do (see XMRV Update, Plus — A Possible New Treatment). In the meantime, it is OK to ignore the debate and focus on the wealth of other exciting new research and therapy advances so you can get your life back now — while we wait for the XMRV question to sort itself out.