I've had the G5X for only a couple of days now, so consider this a working review to which I will add updates as I spend more time with it. However, I think I've used it enough to get a good idea of this camera's strengths and weaknesses.
IMAGE QUALITY: Excellent. Not terribly different from the G7X but that was to be expected given it uses the same lens, sensor, processor. One thing I really like on the G5X is the low compression JPEG option, which gives some really terrific results. I am finding the camera does overexpose a bit in bright conditions, but since you have the exposure comp dial right at your fingertips, fixing that is easy.
VIDEO QUALITY: Have not tested yet. Am primarily a stills shooter so I don't do much with video. I will update on my thoughts on it when I get a chance to try it out.
LCD/VIEWFINDER: Lovely LCD screen and like that it articulates. I find that I am using that more than the viewfinder. EVF is nice and decent resolution. But I do wish it were a bit higher magnification. I would put it on par with Sony RX100 IV's viewfinder. The touchscreen also works great, as always.
AUTOFOCUS/OVERALL SPEED: Sadly, not improved much over the G7X. It's perfectly satisfactory, but this is definitely not a good budget option for action shooting. I mostly shoot landscapes, so it's fine for me.
BATTERY LIFE: Mediocre like the G7X. It uses the same battery, which is unfortunate. Frankly, Canon needs to cut the crap of putting small batteries in powerful cameras like these. You would think spending $750 on a point and shoot would afford you a decent battery.
HANDLING: Mostly good with some caveats. There are three control dials on the camera: One on the back, the adjustment ring on the lens (whose sound has been dampened a bit over the G7X), and that front dial. It's that front dial that I take exception to. I think it compromises the ability to grip the front of the camera a bit. Once you get used to it, it's fine. But I think a better choice would have been to just have the two adjustment dials and just have the grip up front for more comfortable handling. On the positive side, the exposure comp dial is less fiddly than the G7X's. I also don't particularly care for the video record button located within the thumb rest. I don't think it should be located where your thumb naturally rests.
So overall, I like this camera. I do think the extra features over the G7X make it worth the higher price. I think the image quality is superb, and honestly, I cannot tell the difference at low and mid ISOs between this camera and the 18MP APS-C rebels. It's a great alternative for folks considering a Rebel but aren't interested in investing anything beyond the 18-55 kit lens.