Update for windows:
smplayer_update_0.1.9.zip
This version should be able to load idx/sub subtitles.
Meanwhile I've been developing for version 0.1.11 something that I think it could be very interesting.
There are still a lot of options (filters and so on) missing in smplayer. You can pass options to mplayer in the preferences dialog, that allow you to do things that smplayer can't do right now. But there's a problem, those options are global. If you for example add there a crop filter, that filter will try to be applied to all videos you open.
To fix that problem, now you can set additional options for mplayer that will only be used for the current file. That options will be saved, so they'll be used when you open the file again.
And also I've added the possibility of choosing an alternative demuxer, audio codec and video codec.
Tomorrow I will compile this version and upload a binary for windows.
Meanwhile I'll show you some screenshots, so you can get a better idea of what I'm trying to explain:
