It promises to encourage the growth of beneficial bacteria in 7 days, even in less than ideal conditions. Having had experience with it, I believe this is a touch untrue. Because the tap water here is very soft and it is a struggle to maintain a stable pH and a cycled tank, I thought I would give it a shot.
By itself, the Stability did nothing. Ammonia was still at dangerous levels even after two weeks, and I was doing water changes every second day as my bettas were visibly stressed by the poor water quality.
So after a large water change, I added a pinch of crushed coral to my filter, a snippet of media from an established tank, and added Stability per the instructions. My tank cycled in less than a week after that, though how much of it was dependent on the Stability I don't really know.
Personally, I use it in conjunction with mature media, rather than on a newly established filter. There is just too much risk it won't work and any livestock could be harmed in the process.