Dips are more pre-disposed to producing dysfunctional mechanics than most upper body exercises. When performed incorrectly, dips will wreak more havoc on the shoulders than just about any other movement.
However, when executed with perfect technique and appropriate body adjustments, they're actually therapeutic on the shoulders. It's important to master the correct form in order to reap the worthwhile benefits while avoiding the potential drawbacks.
Dan John wants to know if you're making progress. It seems the answer should be simple, but is it? Fortunately, the big guy offers up 3 unorthodox ways to gauge your answer. (Wait until you read about the "pencil test".)