Davis has some room to grow. I don't think his ceiling is quite as high as some others have suggested, but he could develop into a very good backup or a solid, maybe slightly worse than average starter. With a very good team he could probably reach the postseason. I like his ability to extend plays, but he doesn't read the defense as well, and I don't like his arm.
He's had three years in the NFL, although mostly on a practice squad, to learn the game and develop. Most likely what we see is essentially what we get.