Another Issue for the Pros & Cons-Mirrors

Mirror reflections-In a recent Weight Watchers magazine, the issue of working out in front of a mirror was discussed. It basically said that ignoring your reflection "MAY" boost your motivation??? Granted until we are the size we want to be-we do tend to shy away from the full-length mirrors, but not while working out. How would you know if you were in the perfect position for doing the exercise, so you don't injure your back?? Come on-I would much rather make sure my posture is correct in the exercise/weight room and ignore my reflection later! I even have a full-length mirror standing next to the treadmill. I want to make sure I am walking tall! How about you-what is your opinion about mirrors?