Albeit an international leg, I did HKG-PEK earlier this year in CA J (A330). I was expecting the worst (as in, I haven't yet enjoyed any flight that involved going to/from China), and it was quite alright. Irksome passengers notwithstanding, the crew was fine, the food was edible and the IFE worked.

That said, the only tolerable domestic China flight I've taken was with Shenzhen Airlines, and that was helped in part due to having decent food.

Not to mention, you're flying from PEK, so expect a delay (and with that, a more comfortable seat!).