Like painfully slow.  I've mapped a drive on the Windows box to the 1 TB RAID 1 two disk array I use for storage (the Ubuntu installation is on a different disk).  It's controlled by a CERC SATA 6-Channel RAID Controller. Drive X:\ is mapped to /data/media.      When I transfer files via the drive mapping I get 25 - 30 kb/sec. - when I do it via Team Viewer (a remote control application), I get 4.6 MB/sec.  My network information from the Ubuntu box is below - but I don't think that's the problem because of the good speed I get using Team Viewer.

eth0 configuration:  /etc/network/interfaces 

# Generated by hdactl on 2013-02-18 21:11:33 / 1

   auto lo eth0  iface lo inet loopback

    iface eth0 inet static

       address 192.168.10.200

       netmask 255.255.255.0

       gateway 192.168.10.1

       dns-nameservers 192.168.10.200

       dns-search home.com

marc@POWEREDGE1800:~$ sudo lshw -class network

     *-network

        description: Ethernet interface

          product: 82541GI Gigabit Ethernet Controller

          vendor: Intel Corporation

          physical id: 7

          bus info: pci@0000:03:07.0

          logical name: eth0

          version: 05

          serial: 00:14:22:75:a5:e8

          size: 100Mbit/s

          capacity: 1Gbit/s

          width: 32 bits

          clock: 66MHz

          capabilities: pm pcix bus_master cap_list ethernet physical tp 10bt 10bt-fd 100bt 100bt-fd 1000bt-fd autonegotiation

         configuration: autonegotiation=on broadcast=yes driver=e1000 driverversion=7.3.21-k8-NAPI duplex=full firmware=N/A ip=192.168.10.200 latency=32 link=yes mingnt=255 multicast=yes port=twisted pair speed=100Mbit/s

         resources: irq:17 memory:fe7e0000-fe7fffff ioport:dcc0(size=64)

marc@POWEREDGE1800:~$ sudo ethtool eth0

  Settings for eth0:

     Supported ports: [ TP ]

     Supported link modes:

                               10baseT/Half 10baseT/Full

                               100baseT/Half 100baseT/Full

                               1000baseT/Full

     Supported pause frame use: No

     Supports auto-negotiation: Yes

     Advertised link modes: 

                               10baseT/Half 10baseT/Full

                               100baseT/Half 100baseT/Full

                               1000baseT/Full

     Advertised pause frame use: No

     Advertised auto-negotiation: Yes

     Speed: 100Mb/s

     Duplex: Full

     Port: Twisted Pair

     PHYAD: 0

     Transceiver: internal

     Auto-negotiation: on

     MDI-X: Unknown

     Supports Wake-on: umbg

     Wake-on: d

     Current message level: 0x00000007 (7)

                    drv probe link

     Link detected: yes