I was on DL059 San Francisco – Tokyo Narita which got diverted to Sapporo. Great crew kept us as informed as they could and kept everybody calm. The captain "walked the plane" several times to talk to passengers in person. There was one elderly person I think that had medical issues. After about 7 hrs on the tarmac, the pilot tried to fly to Osaka to get better ground support. We made it to the runway but didn't get permission to take off from the japanese aviation authority.
Passengers stayed very calm and helped each other. Some passed out extra snacks to fellow passengers as there was no more food on board. It helped that the plane wasn't very full (1/2 - 2/3 full maybe?) I think we were one of the first flights to let out. The terminal was totally empty as we got past immigration and all counters/stores were closed. I didn't try to leave the airport, but some passengers said it wasn't even possible as the airport was closed.
Somewhat scary about this: The pilot/captain (sorry if I am not getting my airline lingo right) told us that he was low on fuel as we landed and had declared a low fuel emergency. Due to the number of diversions, traffic into Sapporo was backed up. It appears that the spare fuel calculations don't include reserves for mass diversions like in this case. He said several other planes where in the same situation.
I was lucky that my company found me a flight out. The last I heard was that no Delta flight would leave until at least 7pm on Saturday ( we landed around 5pm Friday and got of the plane 1am Saturday I think).
Sapporo isn't a very big airport. I think I saw 4 or 5 747s among many other large planes parked there that night.