mirrored forwarding virtuals: really a performance problem?

Steve - I understand packet filtering is applied very early in the life of traffic passing through the F5 and that excessive use, especially if 'filter established connections' is selected, can cause performance woes. After we upgrade to 11.3.1 we'd like to use bandwidth controllers to prevent runaway nodes in our 'default gateway to F5' networks from causing a disturbance in the force. Do these controllers affect only the virtual servers to which they are applied or is there a lower level component to consider (ala packet filters) where we might be shooting ourselves in the foot simply by enabling them?