I use a Midiman USB one by one.  It is a single MIDI in and MIDI out.
It works well after getting the usual driver upgrade.  There was a
problem with the "universe" I am in, apparently, as the universal
serial port did not work with the original driver.  It was the usual
"known issue" and fixed after calling tech support.  The older serial
port version of the same device was a real pain in several ways and was
slow too.

Spencer Chase
http://www.SpencersErolls.com/