The lesson of the day is that no matter how many times you check to make sure the nails you're putting in the wall are level, it doesn't matter when the hooks on the back of the picture frame aren't level. I'd say that hopefully the wife won't notice, but she always does.
It reminds me of a few years back when I put a big picture of our son up on the wall. I went all out, as scientific as humanly possible, to get that thing level. But as it turned out, no matter how perfectly level it is, it still looks off thanks to the light switch below it that was mounted poorly.