I just had mine arrive yesterday!
I have one of these
I'm using ch57x-keyboard-tool to configure it, because I don't fancy running some random closed-source Chinese code (the manual links to a file on Google Drive). It also means I can move over my config when I switch to Linux.
I have two keys for switching between headphones and speakers, and some set up for shortcuts I forget (like ctrl-shift-e for the network monitor in Firefox). One key types "hello" just because I can.
I've got the large knob controlling volume, and I can click it to toggle mute. The other two are currently set to scroll, but I don't need that as my mouse has better ergonomics for scrolling.
I still have plenty of unused keys and it's got three layers so I won't be running out in the foreseeable future.