He was a good 4th line winger for the Senators last season. It's a 1 year deal for 250k above league minimum. Despite being sent down to the AHL by STL, he should be a lock to play on our roster all year.
There might be a lot of open spots in the bottom half of the Senators lineup. There's a reasonable chance the Senators could be looking at trading any combination of Smith, Hoffman, or Pageau as their names have been in trade rumours this past season. Burrows and Gaborik are not locks to make the NHL, and that's assuming Burrows isn't bought out.
Realistically, the Senators are paying an extra 150k-250k above minimum replacement cost to get a player who proved over a near half season to be a decent fourth liner for them.