This is my first post.

I fly LAX-NRT-LAX a bunch, and have enjoyed the 747 that UAL uses on these legs. I usually try to fly upstairs...15H is my favorite seat due to the legroom and the place to store my stuff to the right. (There is also a strap hanging near the emergency door that you can hang on to.) The seats upstairs that seat guru recommends are good. The forward bulkhead seats upstairs are terrible. (No place to store your stuff, too close to the bathrooms.) In my opinion here are the pros and cons of the upper deck.

Pro:
I've never seen any kids upstairs.
More personalized service from the F/As.
Smaller, more intimate cabin. Almost feels like a private jet.
Upstairs usually has more frequent flyers...not so many knuckleheads.

Con:
The temperature control is usually messed up. Starts out too hot, then gets freezing cold.

The cockpit is upstairs. Whenever the crew needs to use the bathrooms or stretch they close off the bathrooms.

The overhead storage is very small. Half the time my briefcase won't even fit.

It's easy to get trapped when trying to get off. Lot's of pax put their suitcase in the closet, and then when they are trying to get it when they are leaving they block the stairs. We (my fellow company flyers) usually try to get off the plane as soon as possible and then pass as many as we can on the way to customs. (I've had bad looks, but then see them about a hundred people behind me when they arrive in customs. Now that Japan fingerprints and takes photos of all visitors customs has backed way up.

When there isn't a good seat upstairs, I'll usually try to get 26C downstairs. The only problem I've had with 26C is proximity to the forward coach seats. For some reason they put all the loud babies in the forward coach seats. I've heard babies crying for 12 hours...didn't think it was possible.