Annoyingly, I've been so busy with work that I haven't had a chance to use it in anger yet. I'd hoped to compare both side by side at a little festy last weekend, but Phil brought his M32 instead of the Yamaha.
From the few minutes twiddling time I got in the Yamaha last month, it's obviously a much more comprehensive mixer than the QC12, and if you absoutely have to have proper faders, then it's no contest. The display on the Yamaha is bigger, so you can have a lot more information available 'at a glance' than you can with the CQ12, but I've found the CQ12 interface very easy and logical to navigate, and pretty much all of the information you're likely to need while mixing on the hoof is only 1 button press away.
One thing the A&H does that the Yamaha doesn't, is the ability to multitrack record direct to a 32GB memory card. The Yamaha can record stereo to a USB stick or multitrack via USB to HOST, so it's just a bit more faff involved in using the desk for recording.