i find different ways of doing exercises, regarding the 'strictness' of the movement allow for different feelings when training the muscle.
for me like to go really light with them- like plate and a half light at most. i use an underhand grip and nearly stand upright. none of this 45 bullshit. i lean forward and just let the weight hang until i feel it pulling on the bottom of my lats- if i cant feel this my arms are already to involved, and i hold this feeling thru the motion .go light like this and keep your elbows in and you'll be able to actually feel the pinch in the middle of your back from the traps right down to the insertion at the waist as you go thru the motion. im really trying to thicken that crevasse (sp?) that runs up the length of the back.
like i said, thats why i do the movement the way i do it. you could go a lot heavier and pound out big meaty reps and just work the area as a whole too. its doing what you want with the weight to get the desired result.