flew CA F from PEK-SFO last summer on a 744 combi - it was old F, but I read here on FT that the 744s were also being upgraded with new C and F. It wasn't a bad experience, certainly not SQ - the worst part of the flight was the stench of cigarette smoke on the two other pax in F - the first two hours felt like we were in the smoking lounge. FAs were good. Obviously this isn't much help when you are talking C. If I were to do it again, I'd try to stick with UA or another carrier, although know that it's not the end of the world - just a really really long flight.