My experience was much better, but I had to make a big fuss at first:

Grand Hyatt Singapore
Dates Dec 31 - Jan 3
Rate: varied, around $260 US
Room booked: Grand Deluxe King
Upgrade: Club Level Grand Deluxe King
Upgrades available for purchase - No
Check in- Downstairs

I had made plenty of advance notice for my upgrade request, got a nice acknowledgement and then was checked in to one of the poorer GDKs on the 7th floor, no view, over the HVAC vents. I had to take my disappoinment first to the Club Concierge, who showed me her screen- 100% occupancy except in end rooms without bathtubs. Gave up for a while, but couldn't stand looking at the HVAC, so went back downstairs, spoke to the desk supervisor/manager, who said she had to get authority from her boss to move someone, but did and got me a great room on the 17th floor.

Really the rooms are pretty similar, it's only if you care about view and are sensitive to noise, is it worth making the effort.

PS I was offered club access right off the bat.