Subtitles are available, but may need to be encoded in the container. Here's a list of supported files on U.S. models - they may vary by region, but subtitles are an option in most regions.
As for the Internet@TV options, I'm not aware of a browser being available at this time, but I'll be happy to add your voice to the requests for a browser.
I notice when I play mkv video file with PS50C7000 media player, the subtitle does not appear. I have tweak the tools option but no subtitle option available. Like most media player does have this option, I hope Samsung can added this feature as well.
For Internet@TV application, I would like to suggest if Gmail and Yahoo email application can be added like what Galaxy S have. To make Internet@TV more useful, a decent internet browser will be a great application if can addeed too.
Thanks and regards,