I can't believe people still use treadmills. Elipticals are the way to go but they're much more expensive. I always hear about this "walking" thing from middle aged people looking to lose weight. Even at a brisk pace you'll be hard pressed to break a sweat let alone really exercise. Trade in those walking shoes for a bike or a pair of roller blades.
as a middle aged person who walks regularly and has also dropped a few lbs - walking has been effective for me.. and I do break a sweat - dont be so down on walking -