I drove to SF last Friday from the LA area, and took 5-99-46-5, and so added some time to my route. A friend of mine who was about an hour ahead of me took the 5 all the way, and said that even though he was behind a truck, the traffic wasn't bad at all - this was around 8am - and that I should have just stayed on the 5.
I ended up taking 5 home all the way yesterday morning, and had no trouble at all. That could have been because it was Labor Day, though, and less traffic at that time. (It was early morning)
Traffic updates while driving are on 1610 on the am dial.