I've never known anyone who owned a treadmill who used it. 90% of the people who I've known who bought one bought it with intentions of using it to get in shape. After two weeks the treadmill sat and gathered dust for years until it was trashed. I had a friend who exercised regularly and had a pretty good "garage" gym in his basement - bars, weights, benches, dumbbells, etc. We used it all quite often. He bought a treadmill for cardio, but decided that he enjoyed running outside more. My sister got one to get in shape, and actually has started running almost every day---at the city rec center. She'll literally drive 5 minutes to run on the treadmills at the gym (says that it's easier to push herself when she drove to the gym).

Memberships to the globo-gyms can be $10/month. But that's just my opinion.