Stability works, and can be a life saver if for whatever reason ones bio filtration crashes.
Dr. Tim has been in the aquatic industry for many years, and I believe was one of the creators of Bio-Spira, so I'm sure his product works as well.
cycling tanks is way over rated. if you need to cycle a tank then your not changing enough water imo. never have and never will cycle a tank. i just change 50% 2 times and 20% 1 time a week and a never had any problems.
Unless you are using established seeded bio-media on a new tank,
all new tanks go through the cycle process. Bio-bacteria doesn't just magically appear in massive numbers & convert all of the free ammonia to nitrite, and nitrite to nitrate. In a new system they take time to become established and build up in quantity.
The toxicity of free ammonia is highly dependent on both temperature, and pH, so this can also vary GREATLY from one hobbyists tank to another.
A good read on the toxicity of ammonia can be found in the following article posted on the krib.
http://www.thekrib.com/Chemistry/ammonia-toxicity.html
The fact that a fish doesn't die does not necessarily mean that it hasn't been negatively affected by free ammonia.
Short of having enough seeded bio-media to start up a new tank, some of these bacteria in a bottle products are IMO the fastest & safest way to kick start a new set up.