Blu-Ray is a terrible format, and Sony has lied repeatedly about it. I'd rather download HD content to the Xbox360 than ever buy Blu-Ray.
Why? Blu-Ray discs are physically inferior, which the media rights holders (movie studios) LOVE! This means your movies are much more likely to be damaged and require re-purchase. Blu-Ray didn't win in the market place, it won in the business model for the studios and the consumers are screwd. And NO, they don't use the "protective coating" that Sony lied about. It's too expensive!