My experience is only 100% problems with TopCashBack. Failed tracking and vague customer support.

However, I've been a Quidco user for years without problem. [When tracking fails, or there is other cause for support, it has been good and fast.]

As such, my TCB sample size is low. [Only where there has been a rate variation from quidco.]

N.b. The tracking problems are NOT to do with use of quidco or other links, having a slight technical connection to the underlying industry, and (to put it bluntly) 'knowing what I am talking about', the problems appear to be reconciliation ones at TCB.