In my opinion, this is a singularly BAD idea.  For thousands of years,
in Western culture, the dragon has been a symbol of pure evil
incarnate.  Tux, in contrast, does not represent evil incarnate.
Since you asked for postive comments, I suspect your sample will be
skewed in favor of the proposed mascot.  Moreover, I also expect that
a much larger share of the current KDE user base will approve of the
proposed mascot, as compared to the potential future user base.  Thus,
the use of this mascot can be expected to alienate the prospective
user base.  Certainly the direct affiliation of KDE with evil would
preclude my own upgrade to future versions.  As recent mass murders in 
the US have demonstrated, the use of evil symbolism is not a light
matter, for it is a common precursor to evil action.