I wouldn't call myself a huge fan, but I really fell in love with a few of their songs via Rock band and Guitar Hero: "Almost Easy", "Beast and the Harlot", "Bat Country" and "Afterlife"; and I've liked almost everything else I've heard of them... not knowing how important The Rev was creatively to the group dynamic, I hope that this doesn't spell the end of the band.
My thoughts and prayers go to Sullivan's bandmates, friends, and family.