CONS- the plastic seal is hard to remove.  The stuff stinks up your hands and the whole room like terrible rotten eggs.  I wore rubber gloves and washed well with soap after but my hands still smelled for a long time, the stuff also drips on your wrists and arms.  If you have anyone around with sensitive skin, nose you cant interact with them for a long time.  Keep it far out the reach of children and away from food, this stuff smells highly caustic.
PROS- it works on most of the sterling jewelry I tried.  Unfortunately, it does not work as well on some sterling pieces.  Also, one copper bangle is ruined- my fault.