I have pretty much stayed away from Southwest because of their policies, so granted I have no actual experience on them to offer my opinion. I only have to go on what I have heard.
It is great that SWA works for so many people I am sure that is why they are as successful as they are. Maybe it is because I grew up with an airline pilot as a dad, and he was pretty old school when it came to flying. Safety isn't a joking matter on an aircraft in my opinion. Joking about going out on the wing to smoke may be funny but there are a lot of, well shall we say, less than brilliant, flyers out there. Maybe the person trying to open the door just wanted to smoke?

I will say that due to the pressurization, it is impossible to open a door on a 737 in flight, as the doors are basically big plugs to so speak and the pressurization keeps them sealed.
I have watched Airline and frankly was a little shocked at how the airline conducted itself. It was just another reason to convince me that Southwest really isn't an airline I would fly if I had a choice. Being sang to and asked to play games during flight is unique, but definitely not for me. I am sure it appeals to many people and works for them. Growing up flying a lot, I guess I am just used to the reserved seats and a little more business like (read starched) atmosphere on the plane. To each his own.
I would like to comment that the F/As first job is safety as others mentioned. However the F/A, in my own opinion, does not belong in the cockpit for any longer than it takes to do whatever they went in there to do. Their second job is serving the clients, and if they aren't doing that, well to me then they aren't handling all aspects of their job. Allowing an unattended child to remain unbuckled during a pre-landing check is rather scary, passengers shouldn't have to attend to unattended children, unfortunately that is just another duty of the cabin crew.
As I said I have never flown on SWA so I am only speaking of what I feel as I have had no actual experience on them. I will say as long as I have a choice, I will pick another carrier other than SWA. I prefer the reserved seats, and crews on the other carriers. That is just my opinion. I am glad SWA works for so many others. It is great to have a choice.