Kind of tame compared to Yellowstone, but interesting. Our guide, Selena, was excellent. Prepare to smell like rotten eggs! Selena complained that she and her fellow guides have to hang out because no one else can stand the smell.
The most interesting aspect of this attraction was Gabriel's Hole, the only manmade outgassing. A guide named Gabriel was jumping on the surface to show how pourous it was, and fell in! Fortunately, he survived the experience.
A worthwhile attraction if combined with other sights near Soufriere.