I mention this because Tommaso has now produced an animated GIF of the tweaking up of the MC/data Jet energy scale in the CDF analysis, showing how the residues of data minus simulation behave for JES shifts of 0% to 7%. To put this in perspective, you should know that in 2006 CDF published (actually a few physicists from CDF, a dozen of them to be exact, and among them yours truly) an analysis of their Jet energy scale, assessing at 3% the uncertainty on that quantity.
One should also remember that CDF can now verify the agreement of their jet energy scale with simulations to a much better precision than 3%, by fitting the W->jj decay signal in top pair decays when they fit the top quark mass. The current measurements have a precision of 1% on the jet energy scale, in fact. However, one should also consider that the background in the new CDF analysis may be due to gluon-originated jets, which might be subjected to a different jet energy scale with respect to quark-jets that originate in hadronic W boson decays measured in top mass measurements.
In any case, I suggest you to give a look at Tommaso's animated GIF.