Like others have said, it's a touch more than I had hoped, especially after Bozak and Stastny didn't cash in as much as I thought they might, but I still like it and I'm glad he'll be a Duck for a long time. In a year or two I doubt anyone is getting a quality center long term for under 6, so to have him for 6 more years under that number is pretty nice.
Also guessing they paid a bit extra to avoid any trade clauses and bonus money, which I'd say is worth it.