Given how little there is out there in terms of feedback on China Southern, I thought I'd share my experience. TL;DR: Very good.

Our itinerary: Departing from Bangkok with a main destination of Amsterdam, but instead of simple transfers we ended up injecting stopovers in two big cities in China just because it was a great deal and we had never been. BKK-CAN / CAN-PKX / PKX-AMS end of May, and AMS-CAN-BKK end of June. Long haul I booked exit-row seats as I'm 6'3" (193cm) and my legs need to go somewhere.

Booking experience: The website isn't great. I took my time exploring options and generally thought it was ok to explore routing and pricing options, but from time to time the experience yielded completely weird results and payment through the site was impossible for me. I ended up on the phone with their customer service team in China, who booked (for the same price) the same incredible fare and sent me a payment link that did work. Pretty decent English language skills, very friendly staff. After initial booking, I had to go back in myself to add (and pay for) seats. Done. No email. Hmm. So I called them again and they said something didn't go right and I could either wait a few days for them to fix it or they could cancel and refund it. The refund was instant, and I booked again. Called to confirm and it was all fine.

Flights: All flights were excellent despite being fully booked. The planes were in great condition. The seats quite comfortable. Warm towels before departure, hot meals even on short flights and very, very attentive staff. They lacked the smile I'm used to living in Thailand, but they were all very friendly, immediate in filling requests, and seemed very genuine in their attempts to deliver a great service. Aside from the one domestic flight, cabin crew all spoke decent English. Toilets were kept clean. The one thing I found a bit weird was that service stopped 45 minutes before landing and bathroom visits were no longer possible. I boarded with an upset stomach from Amsterdam (too much cheese?) and the crew tried their best to accommodate me and allowed me an exception to the 45 minute rule. (Sorry, TMI?)

China experience: Arriving into China was a breeze: enrolled fingerprints at kiosks and barely spent 5 minutes at Immigration, queue included. Domestic flight was super easy: security is thorough but very swift. Transfer in Guangzhou: although booked as separate flights, our bags were booked through and we already had a boarding card for the next flight, so we had our boarding card confirmed, went through a security check and found ourselves airside once again. The airline advises 50 minutes minimum to transfer, which I could see being sufficient. Airside was quiet, with lots of shops and restaurants at affordable prices. Even saw a few convenience stores.

Because we've been asked about the other travelers quite a few times, when sharing the above with friends: the majority of travelers were (unsurprisingly) Chinese. Everyone was polite, calm and respectful. Toilets were kept cleaner by both passengers and staff than I've seen on many other airlines. There was no noise on any of the flights, except for the group of (Dutch) teenagers on one of them.

We did not know what to expect, but we're very happy to have chosen this airline. I would happily fly them again.