I'm not sure if Ubuntu follows Debian in this regard, but one of the most frustrating aspects
of the way it interacts with the packaging system for me is it insists on deactivating the
network when it is closed. Quite often I've had networkmanager stop the network whilst I was
doing a remote upgrade, and lock me out of the machine entirely.
NM also seems to be unable to cope with a station with a given BSSID changing encryption type.