Actually I had been hit with such a tax on PMUA. And on AA. I have no complaints with the airline passing these through - there isn't any reason that they should have to pay to give me an upgrade. I think at times in the past some of the airports didn't correctly pick up on upgrades and so everything slid by. I do find the idea of such extra premium cabin taxes annoying though - the airport isn't doing any more work depending on the cabin I am sitting in on a plane.