Oh scales! I know the frustration. I myself am forced to use a cheap analogue one that I know isn't giving me the best results. I think it's the consistency that matters though. The whole purpose is to measure the change in your body. No matter what you're using (digital, analogue, measuring, mirror, etc) you are gonna get mixed results when you lose that consistency.
It sounds odd but the period I had the most weight loss was when I didn't have a scale or measuring tape. I eyeballed in the mirror and paid attention to the way my clothes fit and what size I was at. Now I'm totally scale addicted lol...
