So I say don't worry about treadmills and stationary bicycles, since you can go for a walk or ride a bike outside, where it will also be considerably less boring. (Boring/unpleasant is my big barrier to getting exercise.)

I am discovering that the elliptical trainer is a much better workout than are bike rides or walks, though walks with roverthedog are much more fun. (Plus, it's getting cold here, though I expect that's less of an issue in the DC area where Seain lives.)

Oh, and apropos things like BMI and the like, a gym that doesn't spend all of its time trying to tell you that you're fat and ugly when you join is a good idea.