[dman]

You can still do all of that. NetworkManager is far from the only way to get your box to connect to the internet.

[regularfry]

It does have a tendency to intrude if you don't explicitly configure it not to, or remove it if you're not going to use it. I always forget to tell it not to configure /etc/resolv.conf, and always get confused when DNS lookup breaks.

[dman]

apt-get purge it!