Kelly does a lot of things well that you really need your fourth line energy guys to do:
Firstly, he can skate really well. It's a speed league now, and slow footed guys in your bottom six get exposed instantly. Kelly is one of the faster guys on the team.
Secondly, he is tough and not afraid to battle. He is a complete pain to play against, which is again is what you want out of your bottom six.
Finally, he can chip in offensively. This is huge, because come playoff time our top line is going to get checked into the ice, especially on the road where we don't have last change. In the playoffs you absolutely need your bottom six guys to be able to contribute, and both he and Watson can. (This is why I am sour on Gambrell - he does a lot of things well, but he is a complete black hole offensively.)
Anyway, it's pretty obvious that Kelly can look for a place to live in Ottawa this summer, and no longer needs to live out of the Brookstreet Hotel. He'll be on the opening night roster in October...