Volume 1 gives you the songs you hear on Time Life collection infomercials every Saturday night, and this gives you some lesser-known, but still great, tracks.
Ballad of a Teenage Queen is cheesy, as is the studio version of I Still Miss Someone (please please listen to a live version before you skoff at this great song). Bird on a Wire is amazing, as are the songs produced by Rick Rubin, such as Unchained and In the Sweet By and By. The Ballad of Ira Hayes is moving, and Don't Take Your Guns to Town is one that should be played on the aforementioned infomercials. If you're new to Cash, and have listened to Volume 1, give Volume 2 a listen if you're too short on cash (no pun intended) for a box set.