When I used wpa_supplicant, it had better behavior than NM. If I disconnected, the network didn't immediately disconnect and force me to do everything again. I could walk from my room, out to the staircase and to the room above or below me in the dorm on my wireless without reconnecting (manual or otherwise) to my router even though the stairwell was well out of range. NM drops at the hint of a disruption (e.g., power cycle the connected switch) and NM would disconnect wired lines while manual ifup just waits and buffers traffic instead of confusing all NM-aware applications.
Unfortunately the machines I have don't have wireless chips that are supported by upstream, so I'm without wireless most times.
TWC cuts out and this is the quickest way to get the modem to allow traffic through again. It's not the switch since the same happens when the machines are connected directly to the modem in which case a modem power cycle is the only way and the local network is unaffected.