Upgraded on UA several times on Trans-Pacs. I became 3P in July and 2P in October 2008.
Jan 2007 - SFO-LAX-NRT and KIX-SFO: business class, open jaw
Sept 2007: SFO-NRT: business class, one way
March 2008: NRT-SFO-NRT: business class
August 2008: NRT-SFO: business class, one way
Not sure what the chances are now of getting those upgrades, but they weren't impossible.