Hi, i didnt go to Oxford but I did have OATS feedback for some of the subjects and I must say found them to be extremely useful revision aids.
You didnt say which subjects you are going to sit but for me i found the OATS feedback on PofF , Ops Proc, Met, and Performance to be spot on. almost 70-80% of the feedback questions cropped up on teh actuals. That said, DO NOT rely on learning the feedback to get you through... you wont pass.
feedback can be used usually to get a sense of the areas you dont need to be an expert on and that saves time and energy during revision. Dont leave practicing feedback questions til the end and dont forget to practice feedback nearer exam time.