I run the Airport Extreme on BT Infinity instead of the HH3 and I find that it is more stable, no dropouts of the BB connection.
You use the same cable to connect between the modem and the Airport.
I have a printer connected to the USB port on the airport and that is used by the four computers on the network.
The biggest advantage for me though is that the Airport is dual band, 2.4GHz is very crowded here so the 5GHz band is used to connect the iPads and the MacBook PRO all the other stuff uses 2.4GHz the difference in speed for me between the two bands is like night and day. On 2.4 GHz I can see over 35 networks but on 5GHz there is just me and a neighbour.
The HH3 sits in a box under the bench just incase I ever have problems. I don't expect to use it again.