I used a cybex arc trainer last year and found myself ill prepared for Emmons glacier on Rainier unfortunately. I bought a treadmill when I got back and set it for 15% for the duration of my workout and feel a lot better conditioned at this point. Sort of a different piece than a stairmaster but it allowed for incline and resistance in a similar way and as my feet were not completely off the pads it contributed to my false sense of security and fitness going into the climb.
I bought the uphill athlete 16 week program and feel a lot fitter at this point than I did last year. I think the duration of my workouts have really helped. I don’t think I could have accomplished this without a treadmill.