Been doing pretty well with these. Had a couple last year and here's the first of this year:

Hilton San Luis Potosi
Hilton rate: 116/night
Expedia rate: 106.28/night
BRG rate: 79.71/night
9 night stay, it adds up! saves ~350 or so I think

All my successful ones have been with expedia so far. Also, this was my 2nd attempt as while I was waiting on the first attempt, the room sold out! It was the last one of it's type so I tried again with a different room type and was successful. It's really nice to have an upgraded room on work trips.