If your pads ever come out with uneven wear between the pad set, then you've got a sticking piston and its time for a complete overhaul. Take a look at the picture below - one pad is almost worn out (one on the right) and the other is barely worn. An additional tell-tale sign is that the really worn pad is worn on an angle and not flat across its surface - this means that the rotor is bending at an angle because only one piston is moving.



If both pads are worn on a funny angle then your entire calliper is probably not aligned properly with the rotor.