BB is it really good.

[Aquattro]

Running my 75 with a full load of SPS, 5 fish, 70# of rock and no sand, I had 0 NO3 every time I measured. No gadgets, no NO3 removal stuff. 10g water change every two weeks, Ca reactor for Ca/alk and nothing else. No Mg, no supplements, etc. My tank did just fine and grew faster than I wanted it to. The BB allowed much greater flow than sand would have allowed, which results in thicker SPS growth. After 6 months the bottom was covered in coraline and such anyway, so it looked ok.
That being said, I miss the times sitting in front of the tank at 3am with a flashlight watching all the cool critters from the sand bed.
My new tank will have some sand for decorative purposes as well as giving me back some of those critters. I do not consider sand neccesary for NO3 removal, but that's just my experience. I would never use a DSB again, as I feel this is just a time bomb waiting to kill the tank. Might be 4 or 5 years down the road, but it will go boom. Again, YMMV