I have also seen unpredictable black levels and lousy analog output with STB's. CableCARD has made the set a far better one, one remote and I can tune anything, air, analog cable, digital cable, no input switching, no cables.
Terrific idea, whomever came up with it. Hope it becomes the standard, I'm sure the cable companies will find a way to introduce VOD, in fact, the head end said two way cards will come. Anyway, the FCC is mandating support for them, so that helps.