Thought it was just me. Exactly the same situation. My whole collection of audio files are stored as a flac and ape formats and are not playable by rasplex.
I can't believe that no one is interested even to test and report back.
Lack of replies doesn't necessarily mean that no one's interested.
Only a minority of forum members have an RPi to test with (my own is out on loan), and many use theirs only for movies and TV shows. And even among those that also use it for music, some may not have any files in the same formats you use. I'm almost in that category myself, since nearly all of my several hundred albums use MP3 only. I think I have one or two in FLAC, but none at all in APE.
For the record, my MP3 music does work fine through RasPlex 0.2.1, which I tested when last I visited my brother (appx a week ago).
In any case I can't test this further on the RPi myself right now, since my brother has borrowed it (until he can afford other media player hardware). But I'm still interested in any results you may get in this thread.
Inability to play audio files (flac, ape) is a major showstopper.
Plexbmc on raspbmc is playing fine audio files but rasplex is unable to do it.
For completeness it would be good to know if you also have the same problem with MP3 music, or if it only affects APE and FLAC.
(CODEC-independent issue or not ?)
If the MP3 playback does work then you may be able to play the other formats through PMS transcoding.
Unfortunately I really do not have currently any .mp3 files to test with as all of my virtual audio collection is stored either on flac or ape files and I am on the seaside (and the unraid plex server is at home)
Once I am at home I will test some mp3 files and will report here.