As for Sky, I would say it;s been reasonably successful. It's only been available (up to the end of March that is) to those who pay top whack and I estimate that roughly 10% of those customers have activated it. 400,000 homes after two and bit years is not far off the growth of Sky HD (498,000 after 26 months).
So your definition of it being a success is based in your own estimation? Even if it was right how many people regularly watch it once the novelty factor has worn off?
And after 26 months how much HD content was there compared to 3D now?