Easy to use, powerful, very well documented freeware. Who could ask for more?
Cold Fusion Guitar
From the Echo Nest Site: “This is an application that helps you find out whether a human or a machine is setting the tempo for your favorite music. To do this, this application generates a click plot that shows the deviations in tempo from the average over the course of a song. Songs that don’t stray too far from the average are likely to be using a click track or a drum machine to set the beat.”