I can't remember the 10G firewall figures we got in testing off the top of my head, but we didn't max out the 10G network; I think we were getting somewhere in the 8G range. This is significantly better than our OpenBSD performance but not quite up to the level of full network speed or the full speed that two Linux machines can get talking directly to each other over our 10G network. I also suspect that performance depends on which specific NICs you have due to driver issues. The live performance of our deployed FreeBSD firewalls is harder to assess because people here don't push the network that hard very often (although every so often someone downloads a big thing from the right Internet source to get really good rates).

(I'm the author of the linked-to article.)