See URL below from brs on tests they've done using different carbon. ROX appears to be very good. Can never suggest if anything is worth the money. That is always a personal choice .
I tried the Rox carbon a smaller amount did a better job than the cheaper stuff and no dust clear water fast its expensive and the cheaper stuff works good its all about if you want to pay for the best
Easy to use, less mess, virtually no dust. I change mine every two weeks keeps thing looking crystal clear. Follow directions on the label for amounts. Its amazing how little does so much.
I think its worth it. Being acid washed, I think it may be less likely to cause some of the possible issues that GAC may have, including HLLE type issues in some tangs, without excessive rinsing before use.