I don't know about satellite but Time Warner only provides me with a 60Hz HD signal right now so the 120Hz refresh doesn't help yet with cable.
It does help a lot with movies over my DVD player and BluRay. Regular DVD upconverted will play at 24 FPS. If played on 60 Hz TV, then the frame rate doesn't match and the TV will have to fill or skip frames (60/24=2.5). At the 120HZ refresh rate, the TV can process at full frames (120/24=5).