Hmmm...haven't taken a flight yet but I have experienced their customer service as far as making an alteration for my booked flight. I must say, I was pleasantly surprised with speaking to very helpful representatives both using chat and calling in. If there is anything that was tough, it was waiting patiently on hold. The hold part didn't bother me because it wasn't like I was doing anything else in the meantime. But I did finally speak to representative. She took down my information to be able to make adjustments and instead of me being placed on hold for her to make the adjustments, she offered to call me back. I am very impressed so far.
Before I booked my flight, I thoroughly read everything (all the a la cart fees, etc) and am aware of what to expect and I believe just as long as you do the same, there shouldn't be any surprises.
As far as delays, I traveled a lot for business and have yet to encounter an airline that did NOT have delays. It happens. Better safe than sorry.