Test drive a manual and a DSG to see which you prefer. If you prefer the DSG make sure it's had been serviced at the correct intervals (evert 40k miles I think?).
If the car has been remapped the diverter valve may fracture, but this is easily fixed with the latest revision diverter valve which is pretty cheap from VW.
Check for rust at the top of the front arches as some earlier mk5s have problems there. Rare, but it happens.