Yeah SFO-JFK in p.s. biz is a great use, as is a oneway to Hawaii for only 2,500 extra miles on a European award! I was just commenting that OP should probably wait until next trip to take advantage of a free oneway, since cancelling for $150 is not worth it to add LAX-SFO.
By the way, I made a youtube video of how to book these free oneways in case anyone is unaware:
http://www.youtube.com/watch?v=1aj4k4AF5x4
And I agree that there's no point in calling them free oneways when talking to agents. Though I also wouldn't say open jaw with a stopover. I just name my flight numbers and dates without using jargon.