My experience with RM in general is not good at all. This is why at work we use almost exclusivley TNT for anything other than non-important or very low-value bits. What I can say is that TNT are very good and in the 8 years we have been working with them I never had a problem, although we did have issues prior to that with other couriers. For this reason I don't know how how good their claims policy is, because we never ever had to claim...
Problem is TNT (and most other couriers) is not cheap, so I am not how suitable it is for very low value items. One other (sad) option is to accept that RM is a given, try to work-out roughly how much you loose-out to RM incompetance, then increase your product prices across the board to compenstate for delivery loses. Easier said than done, I know, becuase everyone has competitors, but I think it gets to a point where RM loses should simply be regarded as operational costs...
I wonder if they will improve once (if ever) privatised?