I'm watching Sintel now at 1080p. The quality is something I'd expect to see in a movie theater! Previously I've seen Big Buck Bunny, which my daughter loves. :) But Sintel blows it away.
That was the main focus of Sintel. There was a lot of focus on getting the renderer able to realistically handle 4k, which is a resolution standard (stands for 4k horizontal resolution). From wikipedia
As of 2009, the most common acquisition medium for digitally projected features is 35 mm film scanned and processed at 2K (2048×1556) or 4K (4096×2160) resolution via digital intermediate. Most digital features to date have been shot at 1920×1080 HD resolution using cameras such as the Sony CineAlta, Panavision Genesis or Thomson Viper. New cameras such as the Arri Alexa can capture 2K resolution images, the Red Digital Cinema Camera Company's Red One can record 4K, and Sony's F65 CineAlta camera can capture 4K and beyond to 8K 8768 x 2324.
So it is actually twice the resolution you would expect to see in theaters.
P.S. Don't show your daughter Sintel until you've watched it, it's actually fairly sad.
