Fathom allows you to investigate data in multiple ways. It is especially useful when there are multiple attributes. You can make variety of graphs according to what you like to observe. If you select something in one graph, it will be highlighted in other graphs or tables for easier comparison.
Add line or least square line is helpful to find a formula for a set of data, but what I like best is adding a formula and using a slider to find a graph that fits the data that are not linear.
I liked the ability to control the appearance of the cases, but I do think the placement location is a little confusing. I had to use trial and error until the icons lined up the way I liked.