I used China Southern for Nepal trip 2 years ago and i did not feel any problem. I had more than 15 hours transit in Guanzhou and they gave me option of going to hotel. I was more than happy to be out and see arround the Guanzhou as it was whole day there, flight to KTM was in late evening. I got 24 hours visa in 1 minute (its free) and a chinese guy took me to hotel (he did not know single English word). Hotel was pretty good with free lunch. Slept for a while and then took shower and went out with my little camera. It was quite hot ( It more south than Tarai in Nepal, it was arround September 15), but still walked whole day around the city. The city feels pretty dirty and ugly until you reach Kathmandu.

If you are getting out in Gauanzhou, better have some Chinese money which you can use to eat in resturent or even you can buy things there.

I think (forgot) I took only carry on bags and check in is lot easier than in USA.

When i came back to USA, chinese friends asked me, you did not get whores knocking your doors (in hotel). I was surprised Gaunzhou was famous for food and girls ( I just walked outside whole day so did not get anything like that), so if you want get prepared.

I will certainly will go through Zaunzhou next time as well and if possible i will try to get longer transit as well.