I found this great article and graphic today over at Mother Nature Network. If you click on the picture above it will take you to the interactive version on their site where you can scroll over your state and see how it ranks for water-system violations.
Looking at the graphic it seems the good news is that most of the water that we get from water treatment plants and public water utilities is safe. The bad news is that there are still many Americans whose drinking water does not meet safety guidelines. To further muddy the waters, so to speak, there are currently only 91 chemicals covered under the safe water act. There are thousands of other chemicals that are still unregulated and many of these are on the EPA watch list as potentially dangerous to humans. So your water is only tested for 91 chemicals out of thousands that have been found in drinking water.
So while tap water is generally safe for most people living in the United States I would definitely recommend knowing what is in your water. The use of a home water filter can make a big difference in the taste and quality of your water. Even safe water can often have small particles that have not been removed and is usually treated with chlorine which many people find gives the water a poor taste. A basic carbon filter will reduce the chlorine content and catch much of the sediment and other particles to help you get the best taste from your tap water.