The ATI HDTV Wonder is a great card, but only when NOT used with ATI's own software. If you are considering this card, do yourself a favor and get MCE 2005 to go along with it. The MCE2005+ATI combination works wonderfully with the latest ATI drivers.
For the antenna, I support the above recommendation of the Channel Master CM4228. It is a great antenna and the price is one of the lowest for a high gain antenna like that. If you are very far from the HD transmission towers, consider getting the Channel Master CM7777 pre-amp to go along with this antenna.
I am using the ATI HDTV WONDER + MCE2005 + CM4228 + CM7777 combination for a few months now and coulnd't be happier
The MyHD 120 is supposed to be a very good card, but its software does not support full PVR functionality and they have no plans of doing so. So if doing Tivo like things are important to you, the ATI + MCE2005 is a much better option.
Finally, the OTA HD streams are already encoded to MPEG2 ... so having a hardware based card does NOT help in any way as far as the ENCODING is concerned. Where the hardware based cards (like MyHD) come in handy, is for DECODING and that too if you have a low power machine (sub 1-1.5GHz). If you have a decent machine (around 1.8-2.0GHz or more) and a decent video card that can decode in hardware (ATI 9000 or above, preferably 9600 and above) then having a hardware based HD tuner card does not matter that much.
Note that this is NOT true for SD. Since SD signal is analog, having a tuner card that has hardware ENCODING (like the Hauppauge WinTV PVR 150/250 cards) still outshines any software encoders based cards out there ... even with a very powerful machine.
But for recording OTA HD, as long as you have a decent machine with a decent video card, the ATI HDTV Wonder will work very well for you.