If XMRV does not, in fact, play a role in ME then the sooner we can establish this the better; to blindly cling to XMRV as a cause would divert attention and resources away from other avenues of enquiry.

But my concern is that the latest studies suggesting that there's not a link (and subsequent discussion/media coverage) don't address a number of points raised by the WPI:

I've taken some of the key points listed on the WPI website http://www.wpinstitute.org/news/news_current.html
 
  •   The authors of the two UK studies did not attempt to “replicate” the WPI study. Replication requires that the same technologies be employed. The WPI sent reagents and information to several groups of researchers in an effort to support their replication studies. Neither UK study requested positive control blood, plasma or nucleic acids from the WPI.
  •   The collection, preparation and storage of DNA were completely different between the Science and UK papers. 
  •  The low level of XMRV in the blood. XMRV is present in such a small percentage of white blood cells that it is highly unlikely that either UK study’s PCR method could detect it using the methods described.
I've not read any explanation so far why the recent studies didn't follow the Science methodology or why the points raised by the WPI would not cast doubt on the findings.