Depends on how difficult it was. If they hauled the furniture up a flight of stairs, toss them a few bucks. If they drop it at the curb or just inside the door, no. I just had a fridge delivered and carried up four flights of stairs and tipped $50 because it was a huge pain in the ass for them.
As someone who said "hell no" earlier in the thread, asking for four stories with a fridge is an entirely appropriate situation to tip.
Check your delivery contracts, they'll usually specify ground delivery or one floor only. Four is very much above and beyond, and worth the bribe if they'll agree to it.