I also do not think free dining is to blame for the drop in quality of food. I think the dining plan itself is the main cause for that one. Still, we feel we've been able to get quality meals at WDW but hate the homogenization that only seems to increase at many of the restaurants.
We did experience the free dining way back when it first came out. I was excited at this new promotion. When we were done what we decided is that the dining plan in any shape or form is not for us.
Unless it really were free!