Shawn is one of NBA history's most underrated. His +- numbers are so strong, he has single handedly put doubt in the reliability/meaningfulness of that stat. He helped his teams win games as one of the all time great shot blockers, in part because he bravely challenged everything. Fact: opponents' 2pt FG % was lower with him on defense.
He wasn't one of the best ever players neither was he a bust. He was a competent, middle level NBA center who was worth every penny he was paid.