I actually commute every day via 405 and 10. You are right, it's awful during the rush hour, but during non-rush hours it is still faster than taking local streets. A few weeks ago I left work via 405 at 4:45pm and arrived home at 7:10pm, the commute that would take no more than 12-15 minutes without traffic.
I agree with you but temp varies greatly. It often is 30 degrees warmer in the valley than in Malibu which you notice immediately driving over Topanga.