"We have a 32" Samsung that is about 35 pounds. I didn't have any problem with "sag", but I also wasn't able to tighten the wingnut. (That is my little problem). I also have to wonder if the TV with the bit of sag is truly level.
We cannot get the wingnut tightened because of space. This is close to the wall so our hands will not fit behind to tighten it. My guess is that they best way to tighten this is to install the TV, see where you want it tilted to and mark the spot by the wingnut, then take the TV off the wall to tighten the wingnut, then put the TV back on the wall. We didn't bother with it. We left the wingnut alone and let the bottom of the TV rest against the wall at full tilt. Our television is mounted with the top only a 3-4 inches from the ceiling so the angle was okay to view. Today I stuck an empty tube of toilet paper (with about an inch cut off) behind the bottom section of the TV to keep it at a lesser tilt. It's keeping it in place and we didn't have to bother with taking the TV down to tighten it.
One other problem we had, is that we didn't have studs where the bracket needed to be. The bracket is small and couldn't be adjusted to fit onto the 2x4's in the wall. We ended up mounting a horizontal piece of oak onto the wall into the studs then mounting the bracket onto the oak so it would have a solid attachment for the weight. Our 2x4's were really off center so we had to use a long piece of board. it sticks out about an inch from the edge of the television when walking past, but when siting in front of the TV to watch we cannot see it at all."