Don't worry so much about how high you can get the dumbbells, but rather work on taking them out wide. I just do them because I wholeheartedly believe that they add to my shoulder and upper back developement. For those of you unfamiliar with this exercise, it is performed using a straight bar and a narrow grip of about thumbs width apart. While gripping the bar, stick your thumbs out towards each other and space your hands so they barely don't touch. That's a good place to start with finding a comfortable grip.
Some people like to include their shrug work with back day.
I understand the reasoning. However, I like doing them with shoulders for the following reasons. First, my back workouts are incredibly volumous the way it is. I usually do 18-19 sets for back and adding another 4 sets for shrugs would throw me over the edge of overtraining I think. It must be working because I get comments on my traps all the time.