Originally Posted by Sound Devastation

Things i consider "good" characteristics:

Experimentation
Atmosphere
Progression
Passion
Originality
Musicianship - not in a technical sense, more a 'good at what they do' sense.

some are more vital than others IMO. its unlikely id call a band 'good' for progression alone, or a band with passion and not musicianship, whereas experimentation or originality alone may be enough in some circumstances. My favourite bands obviously have all/most of the qualities.