Bill
I actually have both a Motu Express 128 and an Edirol UM-880
Both work flawlessly the vast majority of the time. The only issue I have ever had, and its been very infrequent, is with the Motu "losing" its USB connection - I fully expect that the issue was more Computer related than an issue with the Motu unit and I actually can't remember the last time it happened!
I use these as my main out's for Midi from my computer's, then have expanded them with Midi patch bays, so I can connect all my outboard synths - seems to work great for me.
Of all the midi stuff I have, the only item I purchased new was the Motu Express 128 - all the other units were purchased second hand and all have worked flawlessly.
So from my experience, second hand has always been OK for me.
Cheers
Nigel