I try both with and without. I havent decided which I like better. most random teammates hate me when I take it but I actually do get a lot of smite steals on the jungle. If you are using a single target champ, smite will speed up your jungle, but for someone like amumu, it doesnt help speed up the jungle but it does help get steals on the enemy small camp. ALSO, when you are stealing the enemy alter, if you have a range skillshot to pull a camp, you can pull a monster and smite it while still taking the alter.
So I think it really is effective for most dedicated junglers