May I attach something?
QEMU PC emulator version 0.12.5 (qemu-kvm-0.12.5), Copyright (c) 2003-2008 Fabrice Bellard
On Debian I have "virtio-net" NIC attached.
On pFsense I have "Intel E1000" NIC attached, becouse pfSense won't recognize "virtio-net". Shame..
Measured throughput Client (Gigabit NIC) -> VM (attached to Gigabit NIC bridge)
Debian: ~860 Mbps
pfSense: ~260 MBps
Let's do more tests. Using 2.0-RC1 (i386) built on Thu Apr 14 18:50:50 EDT 2011.