It is a gimick, if your growing a chemical hydro grow it will not help and my hinder your plants.
Two rules about growing with unknown ferts:
1. Do not use it unless you know what it does exactly.
2. Do not take advice from people who's best answer is "I don't know exactly", "I do it because so-and-so said so" or anything similar.
Molasses will not help your grow unless you have organic medium and organic nutes and the microbes in the soil are hungry. There are PLENTY of true sweeteners for bud development and will actually give you a result unlike molasses, and do not depend on microbes in organic grows.
Most of the people who use molasses and claim great results never compare it to a grow without. I have never seen any reason to use it over a real sweetener.
~GG420