I compiled the source of forked PocketSnes core and I must say it works much better! Sound is better in a lot of games along with speed.

If anyone is interested here is the latest version. Just overwrite the file located at ~/RetroPie/emulatorcores/pocketsnes-libretro/libretro.so

I would suggest making a backup of the current libretro.so just in case.

edit: looks like there is some issues with square games. Chrono Trigger and FFIII (us version) both crash after winning a battle.