Lincoln Park Plodders: How accurate is the Nike plus ipod device?

I am having trouble with my nike plus. I have tried calibrating it on several occasions but each time I reset the ipod it gives me vastly different readings when running the same run at an almost the same exact pace. Is anyone else experiencing the problems?

I've found that the accuracy of my ipod nano depends on where I place it on my shoe.  I usually place it under my shoe laces.  If it is parallel to my foot, I get decent accuracy (if I run a consistent pace over a flat course). If it is perpendicular to my foot, or if it slides around in my shoe, or if I vary my pace, it is not as consistent.