I have used HGS and have had pretty good results.
BUT
Dont believe the insane, crazy hype that you see on their sites.
You will not have a 10 lbs yielding purple cindy with buds larger than basketballs and shit.
They are solid strains from my experiences, worth the soil and nutrients to grow, but they arent going to have you sending out a memo to all your best friends about the unbelievable "super" strain of pot you just grew out.
Purple Cindy is pretty kick ass btw, with a fruity mango type smell and taste, hits immediately.
Super Bud is an OK sativa, covered with crystals but nothing incredible.
Black Pearl is the strongest smelling, tasting pot I may have come across, unfortunately you have to like the smell of paint thinner.
My buddy has Clusterbomb (seed I gave to him) drying as we speak, going into jars this weekend, I will see what its like in a few weeks.
He also has one that we have not identified yet (seed I gave to him) because the mix pack is unlabelled so you have to figure it out as you grow.
I have also had a really high fem to male ratio as well.