I can tell you that my mother in law was GIVEN a LeMond Revmaster,......yes given to her in January and she in turn gave it to us. DH had a bike and rides, so he doesn't like to ride inside. We brought it home and I spin everyday, listenting to my MP3 spin download class that is an hour. I ride DH's bike on the weekends while he watched our baby.
I have to say the first time I got on the spin bike, I about DIED after 30 min of just sitting and spinning, no lifts, jumps, speed intervals, hills just sitting.
Well, since January I can go outside and ride for at least and hour and a half...and average 17-20 miles, which I know is not alot to some here, but it showed me the spinning REALLY paid off. I spin everday during the week and ride my road bike on the weekends because of the little one right now.
Sorry, to drag on, but I think that spinning is GREAT endurance training, and I know for a fact with my heart monitor I train almost as hard indoors as I do out with the audio conditioning. However,....it's ALOT more fun riding out on the road, instead of watching Sesame Street and trying to do jumps at a certain cadence.