Echoing many thoughts
ATL-FLL can either be a fairly decent experience or it can be total chaos.
It's all up to the GA and how they handle it.
Two weeks ago the GA said nothing and it was a complete nightmare. I was in F and couldn't get past the Zone 1 people lined up. I could have been loud and pushed my way past, but I just didn't.
Last week, same flight time (ATL-FLL) the GA took control and actually stopped a few people trying to board in PREM with a very nice, "Oh, i'm sorry sir we aren't boarding Zone xxx yet".
Suddenly after two of those rebuffs, everyone backed off and it was a relatively nice boarding experience.
What I also wanted to mention was the clogging of the queue by the "Zone 1" passengers that are led to believe (or just don't read the fine print) that they are the 1st to get on the plane. I see so many of them lined up, AMEX card clutched tightly to their boarding pass very happy to use this "perk".