I have used several USB 2.0 drives on SBS2003, including a SATA "docking station." I've just put an eSATA port in one server and expect to use it with no problems on my docking station (USB/eSATA combo).
BTW, these docking stations seem like a great new backup or storage tool; they let you drop in any SATA drive, 2.5" or 3.5." All you have to do to remove the drive is to dismount it through the "Safely Remove Hardware" tool. My dock is about 3.5x5 inches and 2.5 inches high, and uses external power. Several companies are making these. You can get them for about $30-40.