I used to have a HH3 which was 2.4GHz only and got a good signal all through the house. Then it failed, and I was sent a replacement HH4 by BT. This was dual band. The 5GHz band was fine for the room the hub was in, but signal strength was pretty unusable elsewhere.
Worse, the 2.4GHz band did not give out a very good signal and upstairs my iPhone4s often dropped out of wifi, thereby using up my monthly data allowance for no good reason.
has anyone else seen this? Is the power output of the later hubs reduced - I can find no info on the web about specs like that?