I'm in a rather fortunate situation since I don't send anyone enough sales for them to properly evaluate my traffic and retention.
But if it was me that they had switched to revshare, I would drop them. I like revshare, but I don't like the idea of a sponsor paying me less or differently for the same sales that everyone else is being paid top dollar PPS for. I translate that move as the sponsor saying, 'We don't need you'. Keep in mind, I'm a fairly negative person.