My only concern with the A380 is that if one is forced to divert over the Atlantic to Gander (say), the only place big enough on most of the Atlantic alternates to park it would be on the runway. If the weather for ETOPS alternates is marginal on that day, it could cause big problems for everyone trying to get across the NATs in their 330s, 777, etc. I know the tracks can be flown with one ETOPS (180) alternate if they're in the right place, but it doesn't happen that often.
[Quick edit just to say that I know the ETOPS rules only apply at the planning stage, but if at that stage one of the only two alternates with legal weather is shut due to a 380 parked on the runway, you're stuffed.]
Any thoughts?