Good news for anyone running (or wanting to run) FreeNAS on X10SDV at 10GE... Intel X557 drivers just got backported to FreeNAS 9.3.1. Nightly, but seems to be running stable.
BUILD - X10SDV-4C-TLN2F Build | FreeNAS Community
BUILD - X10SDV-4C-TLN2F Build | FreeNAS Community