This Answer Record contains updated recommended attribute settings to those generated by v1.3 of the Spartan-6 FPGA GTP Transceiver Wizard.
When using v1.3 of the Spartan-6 FPGA GTP Wizard, update PMA_TX_CFG and TXRX_INVERT to the following values:
PMA_TX_CFG = 80082
TXRX_INVERT = 111