I bought a Z3 recently and received it a few days ago. Unlike others who have had issues with the dongle not working after a firmware update, mine updated (both the dongle and the mouse) successfully without problems.

I like the build quality of the mouse. However, I have some problems with it. Firstly, Bluetooth mode allows you to toggle between 3 saved devices. I found it annoying having to hold the connection button and then select Bluetooth and then use the scroll wheel to switch between Bluetooth 1/2/3. Logitech MX Master does this so much better with a dedicated button to switch between previously connected devices.

Secondly, Bluetooth seems to fail to connect to an existing device for some reason and the connection hasn't switched to another device. I have to go into the Bluetooth menu on the OLED screen and then switch to another device and back to the device I'm trying to connect to, just to get it to work again. This happens intermittently. The Bluetooth connection is definitely not as consistent compared to Logitech MX Master.

Thirdly, this is more of a feature suggestion, you guys should take a look at the Logitech MX Master scroll wheel. It has infinite scroll and is very useful and satisfying. It's miles better than the one on the Z3.

Lastly, this is my biggest gripe. The X1 software is terrible. Sometimes, when you configure a button in Simple mode, the same setting doesn't show up in Expert mode and vice versa. They should be in sync regardless of the mode. And at one point, I had configured the buttons and saved to the mouse profile, but the button functions wouldn't work properly. I had to reset the mouse memory and reset the profiles in X1 and reconfigure the whole thing (exactly the same) and this time it works. It just seems buggy and unstable.