Well the postman arrived this morning and the last piece holding me off retiring the MBP arrived.
The Thunderbolt Ethernet adapter, yes it works, yes it really was plug and go. About a minute and a half for a 800Mb file over a 100Mb switch. Seems perfect and only a little cpu spike.
Well worth it. Off to reboot into Windows now and see what happens 🙂
No there are no drivers for Windows 7 so it doesn’t work – and as a byproduct it knocked out the wifi for a bit as well.