I spose I should say something as I have been one of the most vocal on the appeciation thread in relation to sound quality! :)
Disclaimer: Of course everyone has different headphones / ears / karma so people will hear different things. Without wanting to sound proud, I am a sound engineer so I do tend to listen in a concentrated manner and maybe hear certain aspects a bit more clearly than others? Im not saying i have better hearing than others but I do have experience of listening! :D
I usually listen to 24/96 vinylrips, 192 stuff from HDTracks - not so much rock, or indie with Grado GR10 IEM's
I was a little unlucky in that [on my set up] 1.2.3beta sounded perfect
Anyway, In general the later updates I found the bass was far too prominant in the mix. In all songs I was aware of the bass.
When I work on audio I aim towards mastering audio that nothing stands out on. You listen and just enjoy the music. Where bass is needed on certain styles then its there in the mix. Reggie being a good example of this.
Also there are different types of bass - D&B and regiie have very different bass. Anyway, my point was that some bass on the later FW's was too subsonic and for me the 1.2.7 was too muddy.
The 1.2.8 I think is great -in that- it is very neutral, almost too neutral. Its pretty much what i wanted ! BUT there is no power behind the bass now For example on 'Machine Gun' by Hendrix, the drum has quite a sharp but full lush bass hit. On 1.2.8 it sounds weak.
I think for many people the differences the differences are subtle enough to be a non issue but if you have very sensative phones and have good ears the different FW quality can be something of an issue
I must say though the DX50 sounds so so good. The only reason im making a fuss / comment at all is because it has the capacity to deliver a sound that is unparralled and i think perfect...which is a rare thing!