Air China is a pretty basic beast. The leg room is good at 34". The chinese food is plentiful and tasty (avoid chinese breakfast unless you like congee). Service is ..... well they try their best but their english is not always that good so there is ample room for confusion. They don't serve spirits, only soft drinks (beer counts as a soft drink!). The cabin is a bit tatty even on the newer planes with duct tape etc patching up armrests and the like. IFE is definately hit and miss. The sound quality can be poor and unreliable, you'd be better off with your own player, no power points though.On my flight they were showing I Robot which I thought was good. Half way through they showed the inflight health video. when we returned to I Robot they hadn't stopped it so we missed the middle half hour! The 747 and 777 are similarbut the 777 does have a nose camera for takeoff and landing.
Overall as I say pretty basic, butif you take your own entertainment and anything you might need you should be fine. a bit like a US domestic carrier but without the service.
this was on flights LHR