I have no experience with SFO, but The new LAX F lounge is a bit better than the BA F lounge at JFK (since no CX lounge there). It can get a bit crowded in the evening, though, as you're sharing with two CX flights and a few QF flights. Food selection was a bit limited but what they had was good. All in all the lounge compares favorably to other North America lounges, but still a ways from your average CX lounge and not even in the same league as the Wing/Pier.

And it's of course nice for the J passengers not having to take the foolish shuttle bus out to the middle of the tarmac for their lounge.