Share 'is perfect pitch an advantage to a composer?'

I saw that Julie Harris mentioned in a blog post that her composition students "mostly have perfect pitch".  How much advantage does perfect pitch bring to a composer? It's obvious it'll make it easier to quickly jot down a musical idea, or to read one. But music is based on the relative values of notes, not absolute values. Especially after the scale became "well tempered" we can transpose a p…