I have to agree the the extra $50 or $100 last minute fee stinks on international upgrades. I can understand the charge on a last minute milage ticket, but on an upgrade that you're already paying the extra $250 for, I feel that the fee is too much.
I recently changed a flight 5 days in advance and wait-listed for the upgrade when I made the change. Got the upgrade and had to pay the extra $100. Granted it was worth it, but I had to pay the $200 change fee, difference in ticket fare, $250 to upgrade and $100 for the last minute. All of those fees are my fault for buying a restricted ticket (and for changing plans), but the last minute fee is the one that made me mad... especially since I had requested an upgrade on my original flight in time to get the upgrade for free (ie. $250+25k).

As I said, I know I could have bought a full fare ticket, although it still would have been more than all of those fees. I just think that the fee is a little much. Wish that they would waive just that one for Platinums.