Getting better, but a bit hit and miss
ScotRail offer an excellent booking system, no booking or card fees, and a top cashback rate if your journey is within Scotland. The cashback system in the early months of their time on Quidco was a shambles with every purchase tracking at the wrong amount and valid claims being rejected with no explanation. Things have now improved and tracking is now normally extremely fast, and the payments do come through. However, if you buy a Smartcard ticket, this usually does not track. And if you purchase more than one ticket in a single transaction it will tend either not to track properly, or ScotRail will later reduce the tracked cashback to the wrong level. Quidco seem unwilling to take these issues up with the retailer. So, I'd say, it's fine, but only for buying paper tickets for journeys within Scotland, and only buy one ticket at once.