Entertainer's Secret has been around for over 20 years and has been vouched for by the likes of Beyonce, Billy Joel and Katy Perry to name but a few.
In terms of throat sprays, its basically a simple mix of glycerin and aloe vera + some other stuff to make sure it doesn't spoil.
The best way to describe its effectiveness is that it works as a booster, not a replacement for vocal range. Only training will help you there. (check out our upcoming 'find a vocal trainer' page for a vocal coach near you).