Chromecast is able to stream local files through chrome browser but limited to 720p and it depends on your PC hardware to transcode so it might lag if you have an old PC.
The intended usage currently is mainly for Netflix(Requires VPN router)/Youtube streaming which you launch on your tablet to play on the TV without remote. In future, most likely apps like Plex will be supported so you can play local content stored from your tablet/phone.
If you have Apple devices at home, can also consider Apple Tv as it can do everything that the Chromecast is able to do and with more apps available. But if you prefer the lower cost and don't mind waiting for more features to be added, then get the Chromecast.
hmm from the first paragraph, do you mean that, i'm able to stream local content on my pc like .mkv/.avi files that is pre-downloaded to my TV via chrome browser onto my tv using chromecast?
Never knew the browser could do such things, playing files..?
