So, hill sprints completely rock. I hit about 15 hill sprints on a 75m steep hill. In terms of effectiveness for being "in shape," this is probably better than what 95% of the U.S. does in a given week.
Sad but true. Sprinting up a hill is good for you. Here is the secret hill sprint workout program:
Step 1: Sprint Up Hill
Step 2: Walk down hill (saunter, even)
Repeat until strong, fast, and "in shape."