My Mother-in-law lives in Long Beach, actually Seal Beach, and when we set her HDTV up a year or two ago (with Adelphia then) I remember the OTA being pretty good. I just tested it, then had her go through her cable for convenience sake.
Have you verified with other cable subscribers in your local HD discussion thread that you're only supposed to get 4 QAM channels in the clear? And when you record a channel OTA and play it back, watch that channel live via OTA, and then watch that channel live via cable--the cable image is the better one?? (Most will say OTA surpasses QAM.) Which inputs are you using for your Mac and the Charter STB?
Sometimes HDTVs have prickly built-in tuners, especially the QAM tuner--so make sure you verify everything via the EyeTV and Miglia--don't just rely on the Sammy. Check in your thread, get the actual QAM frequencies, then add those channels manually if you have to within EyeTV.
When all is said and done, I suspect it'll still be a Miglia/USB related. But last thing you want to do is go in with a self-fulfilling prophecy in mind.