for me the main difference a Humbucker makes is the lack of noise (hum).
Humbuckers can be very versatile bits of kit. It all depends on their output.
You will see some with names such as screamin demon or Humbucker from hell. These are obviously high output and would be ideal for metal. However those with a lower output say the vintage types would be suited to country, jazz and rock etc.
Have a look at the Seymour Duncan site or Dimarzio. :)