I have one and I have to say they are by far my favorite urchin. I like that they only get about 2" and their spines are short and unobtrusive- unlike the longspines which can be 24"! Urchins are strong and will knock unsecured frags and rocks down, so be sure everything is tied down. Tuxedos are smaller though and I've never had a problem with mine. He will pick up and "wear" shells and anything else he can find to camo himself.
They are algae grazers and this includes coraline, so be prepared to have some munched. It's not enough to bother me.
As for toxins- the only urchin I am aware of that poses a threat to humans are flower urchins- Toxopneustes spp. They are very distinct looking! I pick my urchin up when I have to move him and he's never bothered anyone else in my tank.
Best looking urchin and best pick IMO!