What context does your friend say he is "not good"?
Early on in WAS he had a 1000 yard season. Early on there was optimism that he'd be a complete running back, a 3-down guy. That hasn't materialized. But he has a good receiving skill set and by most accounts has become a solid pass protector. He exhibits a lot of the traits you want to see out of a "passing down" back specifically. Doesn't seem cut out to be a good full time RB like Stevenson is, but in a defined role he seems to project well. In WAS, he had those expectations of growing into a full time guy and in that sense, he wasn't very good.