It is great, I used it in a web application that I wrote at work that shows and let the user edit a graph of building electric, gas and water meters. A button lets you calculate the relationships between meters. For example one meter may be split into two, the sum of the flows thru the two must equal the flow thru the first. So basically I set up a system of equations based on the graph that the user created , solved it using sympy, then show the user the flows thru some nodes (the unknowns) in terms of others. Very uselful indeed.