You are going to get varying opinions from everyone. You just have to read 'em all and make a decision based on how you feel about various reviews.
So....to add to your confusion...
We ate at the Coral Reef back in 2006..it was wonderful. We had great service, wonderful food. The only drawback were the two little kids who were allowed, by their parents, to shove in behind us to get right up next to the tank. We were lucky enough to be seated right alongside the tank. But this was also a spot where others felt it was okay to shove behind us, draping themselves over us, in order to peer right into the tank, up against the glass.
Then, we returned there last Sept. A whole different experience. We had looked forward to repeating our great dinner, but that didn't happen. We went during free dining. There were about 4 times as many large families eating there this time. Many screaming children, lots of chaos and confusion. Our server was okay...seemed to be really stressed. The food was okay, but not up to what we had expected based on our prior meal. And we ordered exactly the same things!!!
It was so noisy in there that we decided to leave without dessert, although we had been looking forward to it. But, we weren't able to carry on a conversation due to the noise level...we had to shout at each other.
I have no basic issue with free dining. But, it does fill up the more expensive restaurants. There are a lot of people who would not feel comfortable paying to eat at some of the restaurants, due to the prices, but with free dining, it almost tends to become a free for all...pardon the pun.
We won't be back again...at least not during free dining. But, we can say that about a lot of the 'better' restaurants at WDW during free dining.