Hi,
we have just returned from our trip using TCD and wnt on their new service using jumbos. If you are going before October(i think) then they will be using the jumbos but not between Oct - April.
We were upgraded at no cost ( probably because of spare seats) to the sunshine upper deck, which is in the upstairs bubble of the plane. The seats and legroom were the same as downstairs but there were only 30 seats up there so although no more comfortable it was quieter.
Having now seen the difference in comfort between this and their first class, if I were going again, I would definitly try to get the first class seats. I had not been on a long flight before and could not rest, ankles/feet swelled up and there was only 1 pull down screen for people to view films ( when they remembered or chose to put them on). I believe that first class have armchair tv screens with choices and I could see that the seats looked massive by comparison.
Hope this helps