I've been using URB on every grow since I started in November. At the end of the grow, I've experienced my cloth pots having only a giant rootball with virtually no soil left. My plants have thrived and have excellent branch strength. I use 15ml/gal for every single watering through plant life until flush, I use 10ml. Great stuff!
I had some humidity issues early on that affected growth, but I was pleasantly surprised to harvest a giant cola with an amazingly pungent stench! I smell it outside of the mason jar! I sampled after 10 days in the jar and it's a very powerful stone. I limited myself to 2 drags from the bong and all is well with the world. I'll try again and hope to get a better yield.
@Wildotter, this was a low-yielding auto flower and had nothing to do with nutrients. I stopped wasting my time with autos (I've had a couple of huge autos) and prefer to take my time with SCROGs. I've since switched to Emerald Harvest nutrients and haven't looked back. Check out my other diaries and you can see what I mean. :)