You can judge how good a bunch of photographers are by what they are talking about.
Really bad photographers debate the merits of the Nikon F4 and the Canon EOS-1. Somewhat better photographers debate the merits of the Yashica T4 and the Contax T2. The best photographers, though, talk tripods, tripod heads, and quick releases.
Philip Greenspun from http://www.photo.net/equipment/tripods/
Talking to a professional photographer at an art festival a year or so ago he was asked how he took his photographs. He responded asking what "The three most important things in photography are". There were a number of guesses - film, lens, flash... none of them right. He then told us his answer - the three legs of the tripod.
There are different types of tripods out there. There are the light weight plastic tripods. These tripods are often inexpensive, and made all out of plastic. The advantage is that they are cheap and light. The primary disadvantage is that they are cheap. In my closet at home there is a graveyard of tripods - some of them have a broken crank - others striped gears (plastic strips easily) and some lack a quick release head (every company that produces low end tripods appears to make a different quick release for each tripod -- good luck finding a replacement or spare).
If you plan on using a tripod for more than a few months, one should look at getting a good tripod that will last. I have seen photographers with tripods that they have had for the past 10 years that are still in perfect working condition. These tripods are generally made by Gitzo, or Bogen and range from $100 to $250 for aluminum legs, $500 to $1000 for carbon fiber legs, and $20 to $100 for the head.
Going hiking, I have learned the value of carbon fiber - by its absence. These tripods can be heavy but they are sturdy.
With higher end tripods, the heads are interchangeable just as lenses are interchangeable on higher end cameras. The ability to select a head gives the photographer the ability to select the most comfortable one for him or her - be this a 3 way pan tilt head or a ball head.
Pan heads are precise tools that allow you to carefully adjust one axis separate from the others. This is of particular interest to photographers who work on architecture or landscapes (there is nothing worse than a crooked horizon on a panoramic camera). Pan heads are also often found in studios where the precision is needed.
Ball heads are less precise though faster to move around thus often used by nature photographers and sports photographers where one wants to be able to follow the action (though, sports photographers often use a monopod rather than a tripod). There are few things as frustrating as getting a fix upon a butterfly with a pan head only to have it flutter off to another leaf and needing to recompose all three axis.