The archos is almost .3 inches taller (Yes the black 'rubber' counts toward height). Also the Karma uses a different style of harddrive so might be a minutly thicker but it is shorter than the ipod and archos.

Also, I gave my father my karma and he loved it. He understood how to use it faster than how to use my brother's 30 gig ipod.

I also find it easier to walk with the karma in my pocket than the ipod. the ipod constantly turns sideways and puts pressure on the headphone jack. With the karma, that has never happened to me.