I do not work for BT and do not agree with their engineers about the Home Hub. None of the following is mean to be nasty in any fahion and is my opnion based on my experience as an independent Broadband consultant. (and thirty odd years in data comms.)
The quality of BT technical staff is not what is once was. They will replace Home Hubs as that is easier than doing proper fault diagnosis. I have heard of people having three or more HHs to fix a fault but the fault still remaining. (If one does use substitution, the proper diagnostic technique is to move the supect part to a known good box to see if the fault moves with the part - not fit a new part and see if the fault goes away.) I guess that once three HHs have been used the BT staff concerned start looking for other causes. However by then the customer has had three HHs, the engineer blames the HHs and the customer thinks that the boxes are rubbish. This is not my experience of the Home Hub.
However my only recent experience of BT technicl staff was the engineer who replaced three BT Visions boxes (All with the same fault out of the box would you believe.) and still failed to fix the fault - which was at the host. I don't blame him I blame BT's appalling techical training these days.
Terry