The display on the Acer C720 has a matte finish instead of having a glossy finish meaning that there is no glare in sunlight, but this in turn means that the colours are slightly washed out although the colour reproduction is still pretty accurate.
Unlike Chromium OS Chrome OS can playback all YouTube videos, it's even capable of playing back 4k YouTube videos. Most locally stored videos are capable of being played back natively, some need a different video player installing from the Chrome web store.
HD videos playback fine given that there is only 2GB of RAM in the C720. The only problem I've come across is that HD videos in .mkv format playback without sound.
Sound reproduction is excellent considering the speakers are on the underside of the laptop. Sounds not tinny and considering the size of them sound doesn't distort at full volume and is extremely loud.
The speakers on the C720 put the top mounted speakers on my Toshiba Satellite C660-15R to shame.
Unlike Chromium OS Chrome OS is capable of playing back music, & with Adobe Flash working it also means that music uploaded to Play Music also plays back.
The Acer C720 Chromebook is an excellent device for media playback while on the move as long as you've ether got your media stored on the internal storage or access to the Internet.
The battery life on the C720 is excellent and will put the battery life of any conventional laptop to shame. I can easily get the quoted 8.5 hours heavy use out of it, even though it's not constant use.