Positive. He's very "meh" offensively, but he's good defensively, makes smart plays at both ends of the ice, is a true/natural centre who gets all the nuances of the position, wins faceoffs, is good on the PK, etc. His offence may be 3rd line level, but he does everything else well. He's not a #1 C, but he's one of 3 pretty solid centres that we have (Bozak, Kadri and Bolland), and he definitely helps us win games. He would be a good #3 C on virtually any team, and a solid #2 C on some teams. He shouldn't be a #1 C, but him playing higher in the lineup than he should doesn't make him a bad player, it's just a weakness of our team that we don't have a legit #1 C (until Kadri grows into the role, at least).
Obviously we'd be a better team if we could replace Bozak with a better centre (Stastny?), but we're still a better team with Bozak in the lineup than out of the lineup. I would like to see Kadri get more shifts with Kessel, and more shifts on the 1st PP, but that's not Bozak's fault, and it doesn't make him a bad player.