the best thing to do on the elliptical trainer is to cross train, too. at different speeds, reps, and on different levels... it keeps your muscles guessing.
those machines do overestimate calories burned. id advise not to go pound some desserts cause the machine says you burn 500 cal
cause its SO easy, believe me, ive been there LOL.
running seems to tire me more, too... but i burn less calories. then again, during step class, i use many different muscles and i blast the calories through resistance training.
ive had fabulous results. what it comes down to is changing it up so your muscles dont get used to it and you dont get bored with it.
and the Y is a GREAT place for that! thats where i work out, too!