All these folks are right. I am a spin instructor, so I teach like drills. My drills are longer than one song- usually about 11 minutes of a drill, then change to a different drill. All are intervals, and all work with increasing aerobic capacity, so quite a few spin ups and lactate threshold work. Some days, I do drills on hills, and other days, I do drills on flats.
I think spinning is great (with the right instructor) when you're working on increasing leg strength, working on correcting leg imbalances, increasing aerobic capacity and lactate threshold, cadence drills, working with heavier resistance and spinning, and breathing.
Spin bikes made by star trac are not as good- like the previous poster said, the 40 pound flywheel is chain driven, so you can just let the wheel spin your legs real fast- whoopdee-doo, I always say. A good spin bike is one that is belt driven- they force you to ride with a smoother pedal stroke, and if you try to ride with too little resistance, you'll definitely feel you don't have good control of the wheel. People learn how to ride with proper resistance and learn how to develop a smoother pedal stroke. The only bike I know in Chicago with that is East Bank Club with the LeMond cycling bikes.
koffee