@awebster:
Check that your interfaces are properly negotiating link speed/duplex; on both ends of each link.
A 100mbps Half-duplex link would produce what you're experiencing.
pfsense reports:
BRIDGEIN interface (wan, em0)
Media: 1000baseT <full-duplex>BRIDGEOUT interface (opt1, em1)
Media: 1000baseT <full-duplex>LAN interface (lan, nfe0)
Media: 1000baseT <full-duplex,flowcontrol,master,rxpause,txpause></full-duplex,flowcontrol,master,rxpause,txpause></full-duplex></full-duplex>
this matches the uplink and local switch port configurations.