Agree with everyone's assessment that domestic flying in China is overall quite positive. I usually fly domestic F, and even short hauls like PEK-SHA puts the US transcon F experience entirely to shame. Only caveats are the reduced baggage allowance, which was mentioned (I usually go about 40 kg over, for various reasons, and that winds up costing my about 250 RMB), the F lounges can be quite crowded and noisy (constant boarding announcements), and on some older aircraft the seat pitch can be tighter than you might be used to. Otherwise, my experience is that flying in China is efficient, orderly, clean, and marked by friendly, attentive service all around.