For me personally the main reason for booking PE (which I did for SIN-FRA-SIN as part of a BNE-SIN-FRA-SIN-BNE itinerary last year) is extra space and more comfortable seat. I like window seats and in PE it is much easier to get out if someone is seated in the aisle seat. Both flights I took were full in PE.

I also enjoyed the excellent IFE screen although the IFE was a bit buggy at times, the noise cancelling headsets were a great addition too.

Book the Cook was nice but the choices could be better, I do agree it would be good if the drinks service was better timed for those using BTC.

I couldn't care less about curtains and seperate toilets as I love going for walks during the flight and often will go the toilets down the back as usually less busy and the walk is good.

I did have champagne offered on both flights, can't remember if pre or after takeoff though.