From a psychological viewpoint... it is now generally assumed that there are two forms of perfection: Maladaptive perfectionism and adaptive perfection. Also considered are the 3 types: self-oriented perfectionism (towards the self), social-oriented (perfection expected in others) and other-oriented (perceived expectations of perfectionism from others).
Maladaptive perfection tends to consist of things like fear of failure, perceived parental criticism, doubts about actions, things like that, and has been associated with lower self-esteem, depression, eating disorders, low motivation, lower performance, anxiety, burnout, drop-out, etc, etc. Adaptive perfectionism is more like a kind of 'striving for excellence' really - high standards, high expectations, striving for perfection but can still be satisfied if perfection is not met - you can still achieve 'excellence' without achieving perfection!
Perfectionism taken the often-talked-out way can often be negative because people never feel good enough. Nothing feels like an achievement, self-esteem is lowered, you constantly put more pressure on yourself to be perfect and in the long run it's impossible. It tends to lead to either burning out, depression and feelings of inadequacy, or giving up trying because you know you won't be good enough for yourself. Perfectionism taken the 'adaptive' way, as a striving for excellence, can be very positive.
/Over-analysis :P