Yup, it works, I just did it in Vegas May 9, 2016, at the palace station,the $20 tip trick worked, I booked the worse room for 114 for 3 nites and sandwiched a $20 bill in between my credit card & license and asked for a “comp upgrade”, the desk clerk took the 20 as a tip & said sure, & I said a high floor/strip view…