We started using 90% soluble humic acid one year ago in our mix.
I am a very skeptical person, but we stuck with it despite no visible results at first (I guess to use up our supply as well as giving it a chance to work.)
Did not notice visible results until this fall. Granted it's entirely subjective and anecdotal, however, our lawns seem to have survived the NC summer better than in past years and look better to boot.
Also anecdotal, but our customers are happier. It might just be marketing (I always point out that we have added humates into the mix this year,) but if the clients are happy, we are happy.
I have not tried Sumagreen, but since humic acid is an integral part of that product, I thought our observed results using humic acid this year might be of some interest to you all.