There are gonna be problems with any courier service, having said that I recently had an RMA handled by DHL, going from my home in London, to Intel in Dublin, back to london, it was handled without a hitch, same DHL driver for both pick-up & delivery helped me fill out the international waybill, and I was able to track each leg of the journey online, so no complaints on my 1st DHL experience, in fact the service was excellent. That was an international return, I have no experience of DHL's domestic service yet.
As for my local City Link depot, I think they had one guy who acutually possesed a Driver's Licence, they were and still are horrendous, consider yourself fortunate if you even get a card through the door, they don't answer the phone, they don't actually like getting into their vans they prefer you to visit them.