As someone who personally uses the Black Diamond in all her tanks, I'm a HUGE advocate for it. Just make sure you rinse it out really well first as some of the pieces float and there is a residue that will cloud your tank for a day or two otherwise. There will still likely be some clouding regardless, but mine settled in a couple hours or so with a thorough rinsing. The dark substrate looks gorgeous though, and brightly coloured fish such as my neon tetras and my bettas all really pop with it. Plus the bright green of the plants against it is really pretty =3
I personally didn't use the Clorax solution though. I just put it in a bucket and swirled it around with a house, drain the water, and repeat for a while.
Some people have mentioned it may be a bit sharp for cories, but I have some on this substrate and they do fine - no barbel damage or anything. Just make sure you get a medium grit. The larger sizes, I believe, do tend to be a bit sharper, and the smaller sizes may compact too much. I believe the size I have is 20/40.
If you have an acrylic tank though, you have to be careful when scrubbing the glass. It won't scratch by being pushed by the current or something, but if you get some caught up in your algae scrubber it WILL scratch. I had someone scratch my 55g acrylic because they caught some sand under my Mag-Float, and I scratched it myself with my hand-held scrubber. If you have glass though, it won't be an issue, and sometimes I even use it as a buffer to scrub off stubborn algae in glass tanks.
I originally had pool filter sand, but I noticed it tended to stain and get dirty after a while, which is part of the reason I switched it. That and I just wanted a darker substrate.