Sorry for the late reply, I missed your message and only just noticed it now.
I flew into Los Angeles from London Heathrow, it's about 11H30M flight time but it felt a lot quicker then that.
I went up to the Griffith centre in the day and the view was fantastic and I didn't notice any smog. Also you'll have to go up in the day if you want to see the Hollywood sign as I'm not sure it's lit? The best bet would be to go just before night and experience both! It starts getting dark in LA about half five/six. Also remember the speed limits are only 55MPH in the US! & you can turn right at red lights providing there is no traffic coming from the left. Also when you go to universal studios (if you do - it's great!) then take the metro as it's about $3 return each rather then pay $15 parking.
It was a bit of both really, the atmosphere and how nice the people were.
I loved the German countryside especially and have even looked into buying a house out there. I was only there over the weekend though, but it was all expenses paid by Audi, which made it even more awesome, love the autobahns and the driving discipline is so much better.
Heathrow is a busy airport but it's not bad at all and quiet efficient, not as efficent as Munich but the Brits could never be as efficient as the Germans!
Are you going to be busting the city? There are some excellent links into central London and I can look into it more for you later. Baggage reclaim was quick and easy to