N.W.
I am recultant to use teen babysitters (my kids are 4 and 5mos). I don't feel that most teenagers are responsible enough. That being said, we are going to try out a new sitter who is 18 and graduating from high school in a few months. She works at the daycare at my gym and the kids love her. We will only use her when we want to escape for dinner or need someone to watch the kids while we are home and doing some cleaning or organizing.
I don't think children should be wet when you get home. I don't think diapers should be put on wrong (it really isn't that hard...). As for the toys, if they are still in use that is fine, but a babysitter should help the kids (yours are old enough to pretty much do it themselves) clean up. I don't expect my babysitters (the college girls) generally to clean or cook. I want them focused on the kids. However, my house is always picked up when I get home and dishes etc done if they have eaten. Also- My Space is NOT age appropriate for a 6 year old. Did you give the babysitter permission to use the computer?
I would try to take a positive spin and be glad your husband is concerned.