High Definition movies have finally come to iTunes for download today. You can rent or buy them for your enjoyment on your iPhone, iPod Touch or Mac. Prior to today you could only access HD movies on the Apple TV.
Starting today, movie fans can purchase box office blockbusters for download in HD for $19.99 from iTunes, and films will be available as iTunes Movie Rentals in HD for $4.99 within 30 days after release. Customers can enjoy these films in HD on their Mac or PC and on their widescreen TV with Apple TV, as well as in standard definition on their iPhone or iPod with video.
This is certainly a great alternative to blu-ray, but it yet to be seen how they compare to blu-ray which is most likely a much nicer picture. You can see the iTunes HD Movies page [here]