I also saw these come up somewhere recently and thought they looked neat, but didn't have enough info.
I'd for sure love to have one, buuuuut... the eating coraline algae thing is a pretty big negative for me, I'd worry I'd need a rather larger tank to sustain enough growth for both the urchin as well as the overall health of the tank.
Apparently they also eat periwinkles, as well as other urchins, and can grow to the size of a softball. They also apparently more or less need high-flow, as they're evolved to live in inhospitable, wave-battered shores.