For a fan, you just get a little taste of how a player's personality really is. However, I would say Kessel was done. Kessel is Kessel, the rest of the world be damned. It's his way or the highway, which doesn't work well in a team environment. If the puck turned over, it wasn't his job to backcheck. If he had a defenseman who wasn't exactly Kaberle, he wasn't about to try and make it any easier on them. He'd just blame them instead. He could of had Kadri as his center. But wait, the world revolved around Kessel sniping...and Kadri might be tempted to shoot the puck instead. Even when the opposing team would take the shot away from Kessel, that was their game. And he was instrumental in turning the players against the fans. The chemistry on the Leafs has done a complete turn-around since they go rid of him. And I think Kessel is starting to wear thin in Pittsburgh as well.
With limited teams to trade with, the deal they got for Kessel is a winner. Kappy might not have the career Kessel does, but I wouldn't be surprised if he already has more friends in the NHL. Kapanen is an exciting player, and exciting players get much more love then players that go out and do their job, win games like Komarov or Martin. The fact Kapanen can be used in a defensive position will solidify his position on a roster that is still failing defensively at times.