Be aware that this is a UIO card and will only fit properly in SuperMicro motherboards with a UIO slot. UIO is apparently just a PCIe slot that is physically reversed, so if you remove the backplate you can mount it 'backwards' (I haven't tested this myself), but it's less than ideal, especially for a NIC where you want the external connections.
That said, if you're aware of that, I think this card should work fine. It's basically just a PCIe switch chip (which is standard and 'invisible' to the OS) and a pair of Intel NICs which are well supported in pfSense.