I bought my APPs 17th of Nov, delivered with 2B576. Almost instantly updated to 2B584, then 2B588 a little later.
In Desember I got the 2C54 update. Almost 4 months ago. This firmware
got pulled just a couple of days after. Since that, no info or new
update. 
Early I noticed:
- Noticably less bass with ANC/Transparency mode turned OFF.
- "High frequency warble" with ANC ON
- Distortion (especially in the left bud) when talking on the phone with ANC/Transparency ON
- ANC noticably weaker
- Just yellow (Adjust or try a different ear tip) with the Ear tip fit test
I have talked to Apple a couple of times, and finally I was offered a
replacement solution. Had to "pay" (reserved on my account) about $200,
which I get back when they have received the old ones.
Received the replacements today, with firmware 2B588, and OMG!
Ear fit test is green, ANC is better, sound is better, more bass and
even bass with ANC OFF is good, no distortion from my own voice with
phone calls.
I still experience the "high freq. warble" with movements (either
walking or chewing for ex), but I think that is because with the
silicone tips are moving a little in my ears. And then the adaptive eq
in the buds are making this warble?! Hopefully the Comply Foam tips will
help for this, when they are released.
This is embarrasing for Apple! Almost 4 months since the 2C54 ruined my (and I guess a lot of others') APPs.