In her article The Great Mojave Scam, KateG states, "We don't know how advanced the hardware is, if it is on a dedicated server or how much space has been taken up by data. All of these factors will effect how the computer runs."
Microsoft have actually provided the answer to some of the points. That said, I do agree with Kate that this seems to have been a somewhat misguided attempt at marketing and will do little, if anything, to boost the public's perception of Vista.