Several years ago, my 3.2 auto got a 'spike' through its electrical system (I think battery related) which basically fried the engine ecu. A firm in Derbyshire attempted to repair it, but found it was unrepairable. I got a used replacement, which was then reprogrammed to the car by an ex Vauxhall auto electrician, and although it generally seemed to work ok, it had odd little quirks (it was about 3 -4 years ago, so I can't recollect exactly what they were now), and although the EML wasn't on, it had clutch switch faults stored (I unfortunately haven't access to the cars paperwork at moment to give the codes stored). However, from the seller, it transpired that the ecu was from a 3.2 manual Police vehicle, so the ecu was then reprogrammed for an auto gearbox, and it has been fine ever since.
Presumably then, as long as it is reprogrammed correctly for the recipitant car, it should work ok. Incidentally, it is now the best performing 3.2 I have ever driven; maybe it's a figment of my imagination, but I have driven a few over the years to make the comparison.....