I don't meant to be a Air China groupie, but I just had not had any bad experience on Air China. From ticketing, lounges, on board service, meals, drinks, everything was acceptable or better. I must admit that I was very skeptical of Air China and for a long time was trying to set my routing to avoid flying them, but so far I have had no complains after many segments. My luck is bounded to run out, or perhaps if I try the back of the bus, the experience will balance itself.
I have had experience on a few premium classes, such as PA, NW, BA, LH, TW, UA, AA, DL, TG, AC, VS, SQ, CX, HP, US, NH, MI, OZ, and many others. It seems to me that the service level really depend more on the individual person providing the service, rather than the airlines. One of the most negative flight I had was on BA in a premium cabin, where the cabin crew that served us appears to have a severe hang-over; another very positive flight was actually on UA in COACH, with service from a Singapore based FA. Of course the vast majority of my BA flight were fabulous, and UA being UA, when they are good, they are really quite good, and when they are not so good, consistency is really lacking. SQ in my opinion has the highest overall standards, and even in an off day, they are still very solid.
The vast majority of my experience on flights are generally positive, and I think Air China is much more like a free-enterprise airline competing in a commercial worlld, than a state-controlled carrier that could care less about turning a profit.