Just took CA 757 from KUL-PEK, and while the service was good, that plane is getting tired.
"Business" is the old old old style with ashtrays in the arms (still smells like cigarettes) and the lav in the back was defintely disfunctional/had overflowed recently. Ick!
There is no seat guru seatmap (nor on the Air China site) but the setup is rows 1 and 2 are "C", rows 11-43 are Y. A year ago I ended up in 32A and I can tell you the pitch was a max of 30 inches, probably closer to 29 inches.
To cap it off, we parked at a remote spot at 6:00 and took a bus to terminal 3 (so much for all those new gates). That same plane probably does the RT every night.
Bottom line, avoid the CA 757's. They do have better aircraft in their fleet.