I attended the Fellowship of the Ring last year at the Bord Gais Energy Theatre and it was fantastic. The O2 was too large and the acoustics were unforgiving for an orchestra. To put it simply, the O2 is an inappropriate venue for a cinema screening because of its large size. There was additional lighting on the orchestra and choir which distracted from the screen and it made it difficult to see the screen during dark or night time scenes.
Having said that the orchestra and choir were amazing and I thoroughly enjoyed the their performance. But I was disappointed after seeing it the Bord Gais Theatre because I knew it could have been better.