This is unquestionably the most movement-specific supplementary exercise for the sumo deadlift. It helps to improve:
Muscular strength
Muscular hypertrophy
Muscular endurance
Upper back strength
Grip strength
Lat recruitment
Lockout speed/strength
Generally speaking, train it once per week during any given 3-6 week cycle. Sets and reps can range from 8-15+ depending on your individual needs and goals. Obviously low(er) rep ranges lend themselves better to strength development whereas high(er) rep ranges tend to be better for muscular hypertrophy and endurance.
Hey, wanna tick a lot of people off? Want to start a flame war, a heated academic discussion, or just a good old-fashioned penis-waving contest? Then come out publicly and say that total body training is better than body part split training.