I would rather walk outside in a thunderstorm but for us flatlanders who try to get in shape for mountain hunting I think the elliptical gives the most bang for your time spent on the stupid thing. It simulates hiking uphill better than a treadmill and especially when you don't have any real big long steep hills around your house since I would rather walk outside with a pack.
I would second smokepole's advice and do it at a gym. A good elliptical or treadmill is pricey and you don't have to house or look at the thing when not in use. Also the gym can do the maintenance.
