Specifically I wanted a stacked bar chart so I could see spending over time broken out by category. So if I had a spike, I could see "oh, I bought a plane ticket that week" and I could toggle categories on and off, and just have a graph with, say, groceries and fast food over time. Excel makes this reasonably easy to do, but you can't do it at all in Mint.

One day I will throw it into an instance of http://redash.io and have more fluent access to the data, since I write SQL-backed graphs in my actual job I'm much better with it than Excel.