Currently experimenting. The idea is to isolate any services where I'm not confident yet in their security/quality. The hope is that if there is an exploit in a given service that an attacker won't be able break out of the docker container and cause damage to my systems.
An example of a service I would isolate in a docker container would be a minecraft browser map application I use. I don't know who wrote it, I don't know who's vetting it, I don't know the source code. I would feel a lot better putting this in a container before I expose it to the internet.
I believe I will follow this process for anything that's not properly maintained (not in an trusted apt-repo or some other sort of confidence) Docker