Oh, i think i have my hand on the problem, if you're using dual screen mode, you need to set it as your primary screen, maybe that way you'll be able to use metro with it. And if it's your only screen i can't find actually any good reason why that didn't work
VLC did work fine. I'm saying that if I'm outputting to my 720p TV, something lots of people do with their PCs, I can't run any Metro Apps by default.
Make sure your drivers + updates are all installed properly, i can't find a good reason for it not launching + VLC and K-Lite Codec are still my first choices in terms of multimedia, so... anyway i'm not that worried about the video app...
Yeah, I ran into problems connecting it up to the 720p TV. Video app wouldn't run, so just loaded up VLC instead.