We got at the hotel about 1:30 PM (one and a half hour before official check in), and while registering asked the attendant for any complimentary room upgrade while giving the ID and credit card; unfurtunately we’ve had a negative answer, but it came along with an explanation; the clerk told us that was a very busy weekend (because of Nascar and other events) and there were no vacant rooms in the hotel, so it made me think that otherwise we certainly had given the room change. The attendant was very nice, told us tips and gave us a map of Vegas which explained it to us in detail, so anyway we gave her the 20.
Before check in I remembered this website. I slipped $20 between my ID and credit card. I handed it to the young girl, and she took it. I asked for any complementary upgrades and she typed away. She said no problem.
She later called from the front desk to ensure the room was okay. It was a great experience to receive a true suite with a separate living room, full size kitchen and movie theater type projection screen.