It's like anything else hard as hell to learn from a book or video. You can pick up a LOT, and straight ninja that shit and start to really utilize it, but it will never be like when you get some actual instruction (and roll with people well versed in the system).
The problem is most people assume it's "The rubber guard" but 10th planet is a whole system, everything is really integrated together you can't separate them all that much because one area might lead you to another. It's a "path". My half guard might pull you to rubber guard, to butterfly, which might pull you to the dog fight, to the spider web, and maybe back to rubber guard or something. Eddie Bravo said it in his book, "if you're looking for a guard that works 100% of the time this is not for you".
If you're going to base your ground game off of the rubber guard, make sure that you base it off the 10th planet system and not just ONE guard variation. That's like saying "what do you guys think of the closed guard?" 10th planet system is solid, but it's not the only thing out there.