I get cardio exercise four times a week almost every week. I am age 56, aerobically fit with a tiny VO2 max and better than average core strength. I try to ride on the road for 2-3 hours twice a week. I use stationary cardio machines for exactly 60 minutes a session for my other cardio. I have a lot of time on LifeCycle uprights, LifeCycle recumbents, Climax stairclimbers and lots of treadmills. I like walking fast on a treadmill on a 13% slope best. I also like the LifeCycle recumbent, warming up at 70 rpm and increasing to 85 rpm.
As long as you use a pulse monitor, a 70 to 80% max pulse rate and go at least 40 minutes; I think you can get an excellent workout on a LifeCycle recumbent or quality treadmill. I think cyclical trainers and stairclimbers require more core strength than someone on a new exercise program is likely to have. I think upright LifeCycles place too much weight on the butt and hurt just like comfort bicycles do on long rides. I think the reclining LifeCycle is easiest on the core. I can easily ride the recumbent LifeCycle when my lower back hurts.
I think a recumbent LifeCycle is the best cardio machine for someone who wants to get in shape. You can watch TV or listen to an Ipod. I agree that it is different from riding on the road. I like it, in part, because it is different.