Having visited Henlow at the OM there, PAYD hasn't improved the quality of service or quality of food at all. The staff clearly didn't understand how PAYD worked, and all that happens is that you end up paying for every little extra option you have e.g an extra glass of orange juice at breakfast? - that's going to cost you.
Word on the street is Leuchars PAYD isn't great either. I can't comment on the JR side of things but from our side, its not a good idea.