I think i have been on a few 747s, we never had any problems with the technical stuff, just the tvs not working, the personal radio system not working, the seat reclining not working, the call bell not working the over head light not working. The duty free stock running out, the cabin staff being sarcastic and patronising, water dispenser being warm, the WCs being smelly or occupied, the queues for the WC, the food being the wrong meal ordered when vegetarian requested 6 months before, the over head luggage falling gout of compartments, the reserved seats being given away and having to sit in a cramped inner seat, the walkways always full of the trolley just at the point you need to join the queue for the smelly blocked WC. The endless stream of kids walking and running and jumping over your legs when you have paid extra for the legroom, the parents who tut at you for tutting at the 15th kid that has jumped over your legs and banged them. The inflight movie on a screen that is only visible if you crick your neck to one side for the duration, the episodes of old BBC comedies they show that were funny once and are now unwatchable because the cabin staff are standing there for 10 minutes waiting for a colleague to go get change. Being ignored by the cabin staff for the remainder of the flight because you complained about any of the above more than once. The knowledge that if you complain a third time the address system from the head of the cabin crew will advise passengers that any aggression towards the already tired and over worked cabin staff will not be tolerated, (that only happened once when I paid �75 or so each for an upgrade and the ground crew gave the seats to their own staff because they forgot about us standing there waiting for the all clear to board.) I am very intolerant when nervous. (sorry Clanad ;( you are all great really)
You should be ok though.