I was traveling HNL-SEA last week and it seemed there was at least one person who upgraded using miles, but whether it was at the gate or elsewhere, I don't really know.
On my flight they were selling upgrades into first for $250, and the cabin went out full. I was lucky enough to get an op-up because someone else had also been assigned to my seat and being a platinum they upgraded me into the last available first class seat.
