With the TG-4, it's been quite promising so far. I've not taken any photographs other than to experiment, so I'll post a few in another thread, when I've got something other than the odd scary selfie!
It'll focus down to within a few cm of the lens, which has needed a macro lens with my SLR. It's hard to focus that accurately when hand held, so I need to experiment with the focus bracketing feature.
The GPS can log where you go, even when the camera isn't turned on. It'll stop after 24 hours, if you haven't used the camera, to save the battery. It only seems to log a point every 30 seconds or so, which is probably adequate for walking, but with my cycle commute, has some minor gaps when I go around a sharp corner. It seems to record track points which are almost immediately on top of the GPS track from my Garmin Virb camera, so quite accurate for a unit with a tiny GPS antenna. It also records what direction the camera is pointing, when you take a photo, using an internal compass, and has a barometric altimeter, which is novel.
(Slightly annoyingly GPSBabel doesn't seem to be able to correctly deal with the NMEA GPS logs that it generates, and ignores the altitude information, but that's a GPSBabel issue, not the camera's fault. The NMEA files appear correctly formatted, as far as I can tell).
You can use its WiFi with your phone, to provide a poor man's remote trigger, and indeed entirely control many of the features of the camera. So far, it seems to only download a slightly lower resolution image to the camera, but that may just be some setting which I've yet to find.
I managed to confuse the panoramic shooting system, and it stitched together the images oddly, but I think that's because I took a silly set of photographs.
The image quality appears pretty good, and on the normal "Auto" setting, it seems to get the exposure correct, with nice sharp images, showing up where I've got stubble.
Like most modern cameras there are lots and lots of features, most of which I haven't experimented with yet, and most of which I probably won't ever use beyond a quick "So, what does this do ... ?".