As Curiosity says, nothing is a substitute for cycling the tank properly or doing your regular water changes.
However, Nitra-Zorb can be useful if you are experiencing problems while running the tank in, so that the fish are not exposed to nitrite needlessly. It's easy to detoxify ammonia (using liquid additives) but it's harder with nitrite (Nitra-Zorb does both). I have seen some people with such high nitrite that they would need to do huge water changes daily to protect the fish - Nitra-Zorb is a less stressful option. Some breeders also apparently like to use Nitra-Zorb in fry tanks so that nitrogen-containing compounds are never present in the water.
It can also be useful if for any reason you wish to reduce nitrate below the level that a water change would accomplish.
I think our technical guys recommend its constant use in new aquariums under the idea that, that way, the fish will never be exposed to dangerous ammonia/nitrite, but there will still be enough of these substances around for the natural cycle to proceed, albeit much more slowly. In my opinion, it should be thought of as a useful back-up if problems occur.