I used it back in December 2019, when some clever cloggs decided to put a stopping pacer in front of a semi fast IET service which I was onboard. We went from being 1 minute late to 24 minutes late for absolutely no reason, literally as the pacer was departing, the IET doors got closed.
I put in a claim for it purely just to try it but to be honest it's not worth it, I paid £19.50 for two singles onboard the same journey, all I got back was less than £4.
In terms of TOC's I don't think it makes a difference, it doesn't drive them to perform better in likes of GWR It's revenue is extremely high so Delay Repay is a few pennies to them.