Hi Paul - yup, I was also delighted to discover it in core! Must have quietly slipped in.
To remove the plugin you’ll have to get into the server and edit your app.yml, removing the line near the bottom which installs the plugin. Then do a ./launcher rebuild app.
As to the data, it depends on how the plugin stores it (there doesn’t seem to be a standard way). Or it might magically just work - or not.
If not, it might be possible to completely retain it with a simple hack, or to export it and re-import it into a new multi-select field. Both of those are pretty hard core sysadmin tasks - the kind you need to pay someone for.
I’d be happy to help you with this if you like (since I’m just down the road). PM me.