Guess I can put my 2-bits worth in, as I was part of the 40 pager.
I followed the trend also by going to deep sandbed. I dont know if they work long term or not, and wont argue that point. I can tell you none of mine did. They always had some sort of algae on them. When I moved twice, moving the sandbeds, they were the stinkiest crap I have smelled, worse than my skimmer gunk.
Now I am an experienced aquarists, I had tons of sand critters to "eat" whatever. I run top line filtration equipment. Never mattered. Most reef tanks I have seen in person, have cyno problems on their dsb.
They do remove nitrates, no doubt about that. I have always made sure when posting on removing my dsb, that I run a large turf scrubber, so nitrate removal is not a problem for me. That way someone does not copy me, just cause I did it. Its up to them.
I do have several inches of fine sand in the back, because of my wrasse. The front has rubble and/or Geo-Marine crushed coral. The animal used to clean it is called Doug Lowey & the python cleaner.
We are settin up a friends new 180 this weekend and his dsb from his 120 is going into the 100g rubbermaid sump. Its unlit this way and can be cleaned if necc. and still provides de-nitrification. His 180 bottom will have a fine layer of the same crushed coral.