1. none of the movies published nowadays is in 21:9 aspect ratio, the closest you can get is the 2.35:1.
2. for movies shot in 1.78:1 aspect ratio (16x9) or any other ratios, you would get black bars on the Left and Right instead of on the Top and Bottom, I would prefer the latter as would most people (?).
3. for a size of 56', the premium you have to pay is damn too high if compared to a full HD LCD projector which could project a 100' with ease with half the price. but of course, you would save up some cash for blackout curtains if you used this Philip's.
4. pixel-wise, it's a 2560×1080p. as i said before you don't have a single movie with this kinda resolution nowadays. if you scale it up to fill up the screen, then it's not 'pixel-to-pixel' anymore.
5. any graphics driver for this monster if you want to pair it with your htpc?