I workshopped the same first two chapters of a novel-in-progress at a writer's conference with two different instructors in subsequent years. The first instructor loved my work, said it was "terrific"; other participants also liked my work (they brought me cupcakes for my birthday). The following year, a different instructor hated my work (same two novel chapters, mind you). Her criticism was blistering; she said it was not a book she would ever buy. Of course, she later admitted, when we bumped into each other in the restroom, that she'd mixed my piece up with another participant's story that opened with a long, graphic rape scene straight out of a Dirty Harry movie. I was too embarrassed to go back to workshop and hid in my hotel room for the duration of the conference. Thing is, neither workshop led to me finishing my novel (I still have hope). Some years later, those same two chapters (I need some new material) got me into the Sewanee conference, so they couldn't be all bad.