The killer feature for me is that it can also be an output device with the right tweaks, so for my use case in triggering long running jobs, the icon on the appropriate button updates to indicate the job is in progress and then again when it completes.

For regular use it talks to Apple Music and shows me next/prev/play buttons, with the current album cover as the play button.

I can use it to adjust my Philips Hue lights or set Home Assistant variables directly.

For work I have the most used intranet sites as buttons (Jira, Confluence, version control, etc).