What are positive and negative characteristics of Napoleon in Animal Farm?

I would say that one immediate positive of Napoleon is
that he is not afraid of seizing power.  At a time when the other animals are gripped by
a sense of what to do in a post- Jones farm setting, Napoleon understands clearly the
implications of maximizing the moment and ensuring that he is able to put his stamp on
it.  While others such as Snowball are more concerned with the theoretical implications
of ruling and power, Napoleon is much more practical in seeing the need to act in a
decisive and intense manner.  This can be seen as a positive.  Certainly, the most
negative element of his character is how he becomes chained to the idea of power.  He
simply falls in love with power and refuses to acquiesce any of it to anyone else.  This
helps to bring out a lust for power that results in the repression and killing of those
who voice dissent.  This has to be seen as a negative.  Additionally, his desire for
power is one where he no longer really even tries to discuss the elements of animalism. 
Rather, he becomes a new form of "Jones" in how he manages the farm and suppresses the
animals.  Here would be another negative element.