I have flown Southwest regularly for ~6 years straight now. I've never had any major issues, the staff has always been nice, there aren't really any crazy hidden fees or other microtransactions, and they have a good drink selection :)
I like the open seating approach, too. It is flexible and I think it actually speeds up boarding.
Has a flight or two been slightly late before? Sure. But things happen, I get it.
On the whole, love 'em.