Municipal water has to get to your house though. How clean it is at the plant doesn't really mean much if you're in an area with bad pipes (and in many places they are).
This won't directly tell you if your pipes are bad (and Atlanta does have some areas that used lead pipes from the county supply to the home) but it's a pretty good indicator of the water quality in my area.
If you're really concerned, it's almost always a better investment to get your tap water tested and fix the pipes than it is to buy bottled.
