Some mixed results for me.

SX-NEC on sunday: The wifi-signal and the portal was there, but the validation of membership / business class ticket simply did not work. Maybe there was no internet connection, logging in with M+B credentials or with name/booking ref both immediately returned with "Could not log in now, try later". I tried a handful of times and then gave up.

SX-NEM on monday: Log-in worked fine and stream package was easy to activate. Around 2 hours into the flight the connection died on me (over Germany) and re-login to the portal went in circles (log in succeeded only to show a greyed out Stream package selector and then telling me to login). I later managed to re-activate using another device.