1. Play external subtitles, although I've found it impossibly buggy but I haven't done extensive tests so it could be useful
2. Play .mkvs although that's experimental and also doesn't work very well
3. More features in general such as pausing without bringing up UI, changing playback rate, stuff like that.
Now if you have mkvs I would recommend using this program on a jailbroken windows rt:
It's a program called ffmpeg and it's ported from normal windows. Make sure to download ffmpeg2.1_ARM.zip not ffmpeg0.6_arm.zip
with this program you can copy the video and audio from your mkv to an mp4 so it can play on your rt if you extract fmmpeg to a folder and then run this in command prompt(include the quotation marks and make sure to use backslashes(\) not forward slashes(/)):
cd "The bin folder in wherever you extracted ffmpeg to for example C:\ffmpeg\bin"
ffmpeg -i "Your mkv for example C:\myvid.mkv" -c copy -map 0:v -c copy -map 0:a "Your output mp4 for example C:\myvid.mp4"
That will also go super fast because there's no compression involved, it's just copying all video tracks and audio tracks from and mkv to an mp4.
In fact if you continue to use this command a lot you speed up the process heaps by making a batch file including these 2 lines of code:
cd "Again, your location of the bin folder in the folder you extract ffmpeg to, for example C:\ffmpeg\bin"
ffmpeg -i %1 -c copy -map 0:v -c copy -map 0:a "%~n1.mp4"
and then put that batch file into your SendTo folder(C:\Users\YourUsername\AppData\Roaming\Micro soft\Windows\SendTo).
If you do that then all you have to do is right click on one of your mkvs and click SendTo whatever you named your batch file and it'll make an mp4 with the same name in the same directory.
As far as snes games go snes8x has now been taken off the store but you can get a port of the desktop app of snes9x from here:
if you have a jailbroken device. Although it is an emulator and it doesn't neccessarily run great so if you have the original surface RT as I do I would stick with 2D games. But test them and figure it out.
In fact if you have a jailbroken device there's a thread here all about apps ported to the RT or native for the RT right here:
If you have any trouble with any of that I'm happy to help.