This has become one my favorite "bodybuilding" back exercises. It's simply unparalleled when it comes to the focused development of the latissimus dorsi, with a special emphasis on the lower portion of the lats. This exercise is derived from Vince Gironda's motorcycle rowing.
The Classic Motorcycle Row
I prefer to use the same movement pattern, but with only one arm. The unilateral aspect of the movement allows for a greater activation of the HTMUs (high threshold motor units) in the lats while also facilitating a fuller range of motion.
The trunk angle basically inhibits the participation of the rhomboids and thus focuses the effort mostly on the lats. The key points are to really get a deep stretch of the lats in the starting position and to aim for your hips with the elbow of the pulling arm.