Well, the results are in! I couldn't wait 7 days...the mess was driving me crazy, so here are the results after 4 days:

Messy family 1: 5 wrappers, 7 socks, 7 spots and 6 weeds: 25
Control family 1: 12 wrappers, 5 socks, 3 spots and 7 weeds:27

Messy family 2: 12 wrappers, 6 socks, 5 spots and 5 weeds: 28
Control family 2: 10 wrappers, 7 socks, 9 spots and 5 weeds:31

It looks like it doesn't make a big difference if you clean immediatly or not.

I also found that happiness level is NOT affected by the messy house. Everyone was still elated!

Here's a pic of part of the messiest house: