I personally fly CA a lot and have no problem with them. Short connections in PEK have never been an issue for me and even with as little as a 1 hour connection I always still have time to stop in the lounge and grab a beer before the next flight. If you have or can get your next boarding pass (Intentional Transfer desk), PEK has a separate line for International Transfer immigration that dumps you back into the terminal pretty quickly. Rarely more than 3-4 people in line and if for some odd reason it's long and your connection is tight, just ask people in front of you to cut in, I've had people do it before when I was waiting and it didn't bother me at all. Now, if you can't get SQ boarding passes before immigration that's a problem and you'll have to go through the full process and into the departures hall of the main terminal, in that case 1h45 would concern me but not be a deal killer, I'm pretty confident I could make it myself.

Post #2 in this thread is pretty informative:
http://www.flyertalk.com/forum/china...ansit-pek.html

I'm not so excited about the SQ 772s, as another poster mentioned above, though it does let you fly directly to CHC and avoid Jetstar which is an airline I avoid at all costs.

Your OW itin with CX is nice, but the cross straight flight on the QF 738 and especially the Jetstar flight following it would make me think twice.