Personally, I don't think these checks would do anything to stop an attack such as the one in Las Vegas. I didn't feel one way or the other about them at first, but after reading others experiences, I don't like them at all from a personal safety view. People have reported late evening knocks on their doors, loud persistent knocking and less than friendly security. I have also read of people getting to the door to find no one outside. All of those things can be intimidating, especially to a solo traveler or a woman traveling alone with children.
I think it's only a matter of time before some creeper will get wise to this and use it as a way to gain entry into someones room. I personally would not open my door to anyone while in the room until I've called the front desk to make sure the person standing outside is, in fact security. I would tell him/her I am calling the front desk to verify his/her identity first.