Well, reading this thread, I wonder if I should continue watching. I don't have STARZ so I didn't see Miracle Day when it first aired, so I'm watching the first episode now and it's decent. It is a letdown from Children of Earth but honestly I'm not sure if anything RTD would do would be as powerful and emotionally draining as Children of Earth.
As for Torchwood, I really enjoyed the series. Yeah Children of Earth was the best season, but I can't help but think I enjoyed the first two seasons more since the tone of it wasn't so completely and utterly dark. Given this thread, I don't know if I will continue to watch Miracle Day (I already miss Ianto and the gang together) but at least I checked out the first episode.