Overall: I had major problems with this airline that resulted in me having a $3000 charge on my credit card for a month and missing an intercontinental flight home.
This was without a doubt the worst airline experience I've ever had. China Southern has a few redeeming qualities (see below) but overall the airline caused me a massive amount of stress. The underlying problem was that their website does not work for me in the US, and it all went downhill from there. I can imagine that the airline works perfectly well in China, but I would not recommend it for US travelers.
-- The China Southern ticket prices advertised on Kayak, Expedia, etc. are wrong: flights were listed as roughly $300 cheaper than they actually were. After spending several days trying and failing to buy tickets online, through Kayak, Expedia, and several versions of the CSAir website (more on that later), I had to buy them over the phone.
-- It takes an unreasonably long time for China Southern agents to do anything over the mail. I was on the phone with them for literally 3 hours to buy tickets. Every time they had to look something up, even something simple, there would be silence for 10 or more minutes.
-- China Southern consists of various entities: a "global" website, a Chinese website (which can be viewed in English), phone agents in the US, phone agents in China...and none of these entities communicate with each other. Because I bought my tickets over the phone, I could not access information about them on the website (even if it was working). Later, when I encountered more serious problems, I often could not get answers from the available agents because some other office had issued the tickets.
-- The ticket China Southern issued to me was a pdf in IATA abbreviation format that was nearly incomprehensible.
-- I was traveling with a companion who was going to go on to Australia after Malaysia, and she had a one-way ticket; her ticket out of Malaysia was not yet purchased. We should have realized that this would be a problem, in hindsight. But China Southern did not tell us until 20 minutes before our flight that she would not be able to board the plane without a ticket to Malaysia. I then had to purchase her a Business Class China Southern ticket (refundable) for almost $3000 for her to get on the plane.
-- It took over 1 month and many phone calls (from Malaysia, so they had to be over skype) for me to get the $3000 refunded. This was partly because it took me a long time to figure out which agency I needed to call to get the refund.
-- I was doing research and had some excess baggage. Apparently China Southern charges an excess baggage fee for each FLIGHT, not each journey, so my 3-flight trip back to the US would have cost $450 for an extra piece. I DHLed it instead.
-- China Southern moved the time of my flight out of Asia 2.5 hours earlier. Apparently they emailed me about this (in one of their difficult to understand emails) some time back in February, but in July when the time came for the flight, I had only my original pdf to refer to. (They never issued me a new pdf ticket). Of course, because I bought the ticket over the phone, I could not check in online. They did not send me a check-in reminder or update email before the flight. Therefore, I had the wonderful experience of showing up to the airport at 1:30am and finding out that my flight was departing in 15 minutes. Of course, I did not make it. I was then rebooked on a flight that got me home 2 days later after a lengthy phone call.
-- One thing I can say about China Southern is that although the agents are extremely slow, they seem trustworthy. I did feel confident throughout that I WOULD get my $3000 refund, even though the process was irritating. The agents who helped me buy that ticket were helpful at the gate even though the flight was about to depart. And I appreciated that I was rebooked relatively quickly when I missed my flight, and that it was not held against me that I didn't know about the time change (I didn't have to pay any fees).
-- My new itinerary after my rebooked flight involved 1 night staying in Guangzhou. The airline provided me with a hotel voucher for that night, and I stayed in by far the fanciest hotel I have ever stayed at, which was awesome. Some of CSAir's itineraries from the US to Asia are advertised as being 50+ hours; if, as I suspect, these involve a built-in night at the hotel courtesy of the airline, these tickets would be well worth buying for those who have time.