Summary: I like this item very much. I wear glasses and, despite the comments of others, have no problem seeing the entire viewfinder - including settings information. The magnification is slight, but since I have several manual focus lenses, it provides just a slightly clearer image upon which to focus. It'll stay on my camera full-time. If it had cost $100, the convenience may not have been justifiable...
Summary: This little gadget provides a little dab of magnification, helpful when trying to focus precisely. (Of course, if you want to focus precisely, you should also get a KatzEye focusing screen, because otherwise you'll be looking at a stock screen, which is difficult for manual focus, only a little bigger.) My lone complaint is that it needs to be a little more powerful -- 1.4x or 1.5x would be about right.
Slight magnification, keeps nose away from LCD, still 100% view
5 May 2014
Summary: Although this piece makes slight imrpovements, they are worth the price. The slight magnification is still significant, helps for sharper focus control when focusing manually. This eyepice does help to keep my nose away from the LCD screen. To my surprise, I did not notice any cutting of the viewfinder field as reported by some customers. With 85mm lens on D7000, I did not notice any difference except slight magnification.
Summary: I was getting tired of taking flower macro shots only to find bugs or spider webs on the them only after getting back to the computer. I discussed this with another user and decided it was a cheap experiment. I couldn't be happier. As one with failing vision now, this lets me see way way more of the central detail. I actually saw something before taking the shot that could be fixed after using this.