Well grizbiz, If the antenna is in good working order, and your local signals are in its sweet spot, it will work for you. I've set up digital converters for people with roof antennas, and the main issue sometimes is that the transmitters are in a different place, so you may need to rotate the antenna.
As to basic cable, I personally have the grandfathered analog cable from my local provider, and they recently downconverted all the free HD QAM signals to Standard Definition in all its glory (not).
So I am getting a Zat 502 HD to provide my HD, in addition to the local cable.
I live ~16 miles from the towers, so I get my HD with rabbit ears...