Not so desirable seats
23B/D/F/H - can be a bit of traffic from crew in particular on the F/H side

26B/D/F/H - can get either bar noise or galley noise

Rows 29 and 30 - no enhanced lighting cabin system, generally last to be served meaning you have a higher chance of missing out on your meal choice though on supper flights not usually a problem, a lot of traffic and 4 bassinets near by

11 B/J - can get a bit of toilet traffic and noise

Desirable seats
Row 16 - exit rows with no seat in front and easy aisle access without having to step over anyone.

Otherwise all the other seats are pretty good

Some other information
Upper deck usually finishes before the main deck
Upper deck has a better passenger to toilet ratio 42:2 main deck 22:2 upper deck but remember you can use any toilets but most people don't move between main and upper
Upper deck flooring tends to be a lot louder when people walk past than on the main deck
Upper deck feels more private
Upper deck has side storage so you don't have to reach the overhead lockers if your at a window seat (as mentioned by QF009)
Passenger to crew ratio is 10.5:1 on main deck 11:1 on upper deck