We are still working on walls upstairs, so there is nothing hanging on the walls. Theresa has a huge Doctor Who poster that was sitting against the wall for months and we decided to try those command picture hanging strips after seeing the commercials. I figured it was just velcro, but it is a bit different. There is not a fuzzy side, both sides are the same with the hook part of velcro. The hooks are shaped like a T. They hold well and are easy to separate. Well worth it and we will be getting more for sure.
We put the strips on the back of the picture, used a level on top of the picture, and stuck it to the wall. The picture is very level, but apparently our 106 year old house is not >_<