That "some" are the ones who use it properly.  The stairclimber's ability to get the heart rate up is similar to that of the elliptical. Remember, cardio is about heart rate elevation - let's keep it simple.  It doesn't really matter WHAT you're doing, as long as your heart rate is at a certain level for a certain period of time.  Some activities lead to imbalance in the muscles when used exclusively, which is one of the reasons why variety is key.  The other reason variety is so important is to give your body a challenge.  If you are someone who runs exclusively, you may find the elliptical challenging for the first four times you use it, for example.  This challenge keeps your body fit on many levels. Try to stay conditioned in many different activities - you don't need to perfect one stream (unless of course you are an athlete with a concentration). The stairclimber is a great option because you don't have the same forward movement as you do with cycling or running, therefore the hip flexors don't clench up the same way.  Your movement is up and down, like in jump rope.  Aside from the calves tightening up somewhat, it is an anatomically-friendly workout.  We all climb stairs, right? It is representative of a natural physical activity.

The only problem with this piece of equipment is how easy it is for people to misuse it! I see people taking teeny tiny steps really quickly, I guess supposing speed will equate in a higher heart rate.  This doesn't necessarily work, because when you're tapping the balls of your feet repeatedly, the muscles doing most of the movement are the soleus or the gastrocnemius (the lower and upper calf muscles).  These are relatively small muscles, so they don't require the heart to pump as much blood as do the quadriceps and glutes.  Also, don't keep the speed so low that your hips shift from one side to the other, while the pedal drops slowly all the way to the bottom.

Make sure that you stay in the middle, between the very top and the very bottom, throughout the entire workout.  You want a large range of motion - as large as possible, without hitting either restrictive point (top or bottom).  This way, you will reach a fluid momentum, while using the largest muscle groups fully.  Push down through your heel to target the glute - and work hard! The stairclimber isn't meant to be a "break" - it can be an incredibly powerful cardiovascular workout.  Your speed will be lower than the elliptical in most cases... for best results, use a heart rate monitor for all of your cardio activity, so that you know you're getting the best possible workout for your goals.

And if you have never tried this piece of equipment in the gym, I suggest you change that pattern!  In fitness, change is often very re-motivating.