I use a #7 optivisor all the time. In fact, it's typically on my head. Sometimes I keep it positioned such that I can look through it or below. It's become something I don't even think about. I do remember that there was a bit of an adjustment getting used to it, though. My employees often have trouble with them as well. I think it just takes a bit of time...
I remember taking an engraving class with Wallace Gusler, quite a number of years ago. I'd engrave with no magnification and could see just fine. Those days are gone!
Jim