I use to fly Southwest whenever the option was available. It was the best airline, for an unbeatable price.
The past 6 times I've flown with them, I have been hit with delays every single time. This last time was icing on the cake, as I arrived 20 minutes before takeoff and was told I would be rebooked to a flight 12 HOURS later than expected because they needed to do "paperwork".
Southwest Airlines is not even good for the price, now. It's bargain bin flight, and you'll be treated as a bargain bin customer.