Here is my own two cents on the beta.
Booting up/Shutting Down has a roughly 25%~ speed increase. (Which is about 4-6 seconds!!) Good job FiiO!
Songs scanning will not complete, it hangs for about an hour (yikes) and halts in the middle of scanning and say it is complete. Not surprised since this is a beta.
Sound Quality has become somewhat more treble oriented. The sound signature feels V shaped somehow, it's a mixture between oval and V, think antler horns if that makes sense.
FiiO stock app crashes often, the past FW seldom crashed.
Song list fails to load, selecting a song does not work about 60%~ of the time.
FiiO stock player can now play odd sample rates, at the expense of being sped up, very similar to how iTunes does it at frequencies below 44kHz (etc 31.7kHz, 36.8kHz). Very strange, thinking myself that it would never play these files in past FW version, if these frequencies become supported, I will be so happy, I do not expect it though
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Once again, this is a beta, so I'm reporting on what has happened to me personally.
Will update, since I'm using the stock app for now. I haven't rooted yet, I will get on that right away!~