I've done about 6 RB which have resulted in a couple of good overnights at a good rate. Even if they were all a waste of time £12 for the novelty isn't much out of the punting budget.
Of the others, one was a stupid idea which I binned after a day, a couple were shit punts, the other I had already agreed with the woman prior to the RB going up and I didn't get a better offer.
If you want an overnight they are very good, better if you can point a regular in that direction to try and negotiate a rate. They do seem a bit pointless if you're trying to get a £150 pro$$ie to bid on a £100 booking.