I've ordered from them. Once.
Their prices are great. I would probably go back for the hardware. Everything was packaged properly, labeled well, etc.
But out of the dozen bottles I got, I didn't find anything I'd consider great. Some of them are usable. Some of them are destined for the trash. Out of the 12, there was only 2 I'd consider using on a regular basis. Greenhouse One taught me that a great price isn't really a great price if half of it is going in the garbage. They also taught me to place tiny orders for your first order from a vendor. Of all the things I've tried with ecigs, that was the order I regret the most.
Now this is just my personal opinion, and there are some people who have no problem with Greenhouse One. But I'm never going back. I'm sticking with Backwoods Brews, and DIY stuff.