I just picked up a pair of these cards and was pleasantly surprised to see them supported in version 1.231 (I was expecting to have to use the beta).
The exact card model is PWLA8391GT.
dmesg output for the really curious:
em0: <Intel(R) PRO/1000 Network Connection, Version - 1.7.42> port 0x9800-0x983f mem 0xec000000-0xec01ffff,0xec800000-0xec81ffff irq 11 at device 13.0 on pci0
em0: Speed:N/A Duplex:N/A
em1: <Intel(R) PRO/1000 Network Connection, Version - 1.7.42> port 0x9400-0x943f mem 0xeb000000-0xeb01ffff,0xeb800000-0xeb81ffff irq 10 at device 14.0 on pci0
em1: Speed:N/A Duplex:N/A
I did have a problem with the second one not showing up while in the 3rd pci slot, i had to move it to slot 2 before it showed both cards.