They really are. It's hard to come up with good exercises that offer more than the old "run stairs" trick. So you should try jumping pistols. Go up the stairs on one leg, then come back down on the other. Better yet, do this for every set of stairs you see, like hill sprints.
Something we also discovered, not really necessarily with ptossing but more for parkour, is using stairs to practice light drops and rolling. Start at the bottom and when you get a few good drops, move up one stair. Keep going until you can no longer safely do them or until you get the top. Yeehaw buddy!
Another good thing to do, especially for winding stairs, or stairs that might not be too wide, are frog jumps. Get into a deep squat and don't do a full squat jump, just come up enough to get to the next step. So you'll be in a deep squat position the whole time. These is a great exercise for Precision Jumps (parkour). Did them just yesterday.