I loved the Panasonic GM5. This is why I sold it.
My thought when I bought the GM5 was that it would be brilliant to have a camera so small that I could bring it anywhere while at the same time being a proper camera with a large enough sensor to get really good image quality. I previously owned the Panasonic FZ200 which is a superzoom with a bright lens, but a small sensor and hence the image quality wasn’t very good. The GM5 was exactly as small and portable as I wanted while also delivering good image quality and the possibility to switch out the lenses which gave me more flexibility.
I used it a lot and generally had it with me at all times when not at work, but there were a few downsides to this camera that convinced me to switch. While the image quality was good, I had trouble hand-holding it still enough because of the ergonomics. I tried buying the optional handgrip to alleviate this problem, but the camera was still hard to hold and I ruined some shots because of shake. I also found it hard to use over longer periods of time because of the ergonomics. I usually had to keep my little finger underneath the body since it was so small in height.
Even if in theory, a very small and portable camera seems like a really good idea for walkabout shooting, if the ergonomics doesn’t fit your hand, the camera will be annoying to use over time. In addition, the lack of sensor-based stabilisation that could have solved some of my shake problems caused by the ergonomics was also a negative factor when all the newer cameras from both Panasonic and Olympus have built in sensor-stabilisation.
Otherwise, I found the GM5 to be a very competent camera. It doesn’t have 4k for filming or 4k picture modes like many of the larger and newer Panasonics, but that is probably because the processor is less powerful, smaller and unable to do heavy lifting because there is not enough surface to get rid of the extra heat produced. It’s one of the few compromises of the small form factor. Most other features are more or less the same as on other MFT cameras. There are also fewer and smaller dials and function buttons due to the small size, but for me that wasn’t that much of a problem as the back dial performed double duty. I could press it in and change its functionality. For instance in M mode, it could be used for shutter speed, and then after a press also for aperture. That being said, now when I have more function buttons and dials on my GX8, they do provide easier and faster access to often used functions and settings and I enjoy using them.