The Jazz have been really needing someone who can shoot. Fisher brings a ton of "grizzled veteran" leadership. He has been on so many teams with players better than him as well. Fisher doesn't rock the boat, he knows his role and plays tough defense.
He'll go great with Sloan.
On the other hand, this does not necessarily change the Jazz's position in the playoff hunt... Fisher will put in 15-20 solid minutes a game. His most important role will be in the development of Deron Williams.
This is the kind of guy who comes out of nowhere to hit a big shot in a big game, not really a go-to guy.