I know I've been wondering about getting an elliptical. We have a Tony Little "Gazelle" in our house and my other half uses it faithfully 5 days a week for 30 minutes and lost 50 lbs and has kept it off for 3 years. It is zero-impact on joints, etc, too.
I check Craig's list regularly for ellipticals.....You can get good deals there from people that had "good intentions" buying one but never really use it and want to get rid of it so it doesn't use up space in their house anymore.