Is it possible to know what subtitles are available for each movie (english, french, spanish...)?

Unfortunately, not at the moment.

There's only a limited amount of information that we can pull from the Netflix API, we're looking into if indeed it's possible. Awesome idea though.

Found this link,  if that can help : http://movies.netflix.com/Subtitles.

This would be a killer feature, in my opinion would be the best feature to implement. Because that's the biggest problem is a lot of movies have subtitles you can't remove, it would be amazing to know before hand instead of finding out the hard way. 

There's only a limited amount of information that we can pull from the Netflix API, we're looking into if indeed it's possible. Awesome idea though.

Update: We're still looking at if this is possible - we haven't forgotten about you :)