I don't mind one that's not new, but I believe there is a bit of work installing them so it would make sense to put one in to stay, therefore better not to risk one that may also have problems.
Then again, depends on how much I can get a second hand one for - I already borrowed one off Ray last year just to check against the mess that the japanese owner had left - used to be able to stall the car by jiggling (hmmm...images non car related come to mind!) the harness near the ecu.