Reporting on the experience…
All together it was not bad. Some weird things (only German newspapers and magazines for instance – breakfast 2 hours before landing on a 4 hours very early morning trip that took off at 4:30 am, …), but great crew. Average food.
The seat is as mentioned a lie-flat bed. Interestingly you have to play with the command if you really want it to be flat otherwise it comes back a bit and is no more flat… Massage function was a joke. I didn’t play much with the IFE since it was a 4 hours night flight.
Will I do it again? Well probably not as the schedule was weird (but I had no choice) and transiting in FRA is still a nightmare. Next time, BA & T5!