I have an upcoming stay at the Hilton SF Union Square. Sent a polite email asking about suite availability and explained why an upgrade would be appreciated for this particular stay. Here's the reply I got:"Thank you for your interest in a Suite upgrade. Complimentary upgrades for Diamond members is to next tier level and is done at time of check-in based upon availability.At this time, we do have Junior King suite upgrades available at an upgrade fee of $50 per night or Skyline View – Corner King 1 Bedroom Suite at an upgrade fee of $150 per night. Please let me know if you are interested with moving forward with the upgrade." Despite this being an old thread, like the OP this is the first time I've been asked to pay for a junior suite upgrade. Have been upgraded to plenty of suites over the years.... granted, mostly outside the US.