I hate running uphill as I'm not fit enough yet. I tolerate running on the flat for the smug feeling when I'm done.
HOWEVER... I totally love running downhill. I run at full pelt as though someone is chasing me, and feel very free and almost giggly. The knowledge that I might fall at any minute only adds to the excitement.
I think there's a gap in the market for someone to drive people like me to the top of hills so we can run down them.