I don't have any problem with iLBC except that I need to unmute the speaker before recording (I don't know if this is also needed for the other formats).

I don't know how you replay iLBC files, but the only way I've found is to use Maemo Recorder itself (and to convert an iLBC file into another format, I use a cable to the input line of my PowerMac and Audacity to record the sound!).