If you want a comparison, I have run a small OpenBSD router under KVM and it easily sustained 80Mbps. It was connected to a FastEthernet switch so it couldnt actually go much higher. This was using the emulated e1000 KVM device and OpenBSD 4.9 release with mpbios & iic disabled (disabling iic removes some annoying boot messages). The KVM server was a modest 3Ghz Core2 Duo with 4Gb RAM and a lot of other VM's running.
Cheers, Lars
