Seconding kodos96. As this would exonerate not only Knox and Sollecito but Guede as well, it has to be treated with considerable skepticism, to say the least.
More significant, it seems to me (though still rather weak evidence), is the Alessi testimony, about which I actually considered posting on the March open thread.
Still, the Aviello story is enough of a surprise to marginally lower my probability of Guede's guilt. My current probabilities of guilt are:
Knox: < 0.1 % (i.e. not a chance)
Sollecito: < 0.1 % (likewise)
Guede: 95-99% (perhaps just low ...
The title says it all.